diff --git a/cms/djangoapps/xblock_config/apps.py b/cms/djangoapps/xblock_config/apps.py
index 92271608f684..ae04e3f54793 100644
--- a/cms/djangoapps/xblock_config/apps.py
+++ b/cms/djangoapps/xblock_config/apps.py
@@ -19,9 +19,9 @@ class XBlockConfig(AppConfig):
     def ready(self):
         from openedx.core.lib.xblock_utils import xblock_local_resource_url
 
-        # In order to allow descriptors to use a handler url, we need to
+        # In order to allow blocks to use a handler url, we need to
         # monkey-patch the x_module library.
         # TODO: Remove this code when Runtimes are no longer created by modulestores
         # https://openedx.atlassian.net/wiki/display/PLAT/Convert+from+Storage-centric+runtimes+to+Application-centric+runtimes
-        xmodule.x_module.descriptor_global_handler_url = cms.lib.xblock.runtime.handler_url
-        xmodule.x_module.descriptor_global_local_resource_url = xblock_local_resource_url
+        xmodule.x_module.block_global_handler_url = cms.lib.xblock.runtime.handler_url
+        xmodule.x_module.block_global_local_resource_url = xblock_local_resource_url
diff --git a/lms/djangoapps/lms_xblock/apps.py b/lms/djangoapps/lms_xblock/apps.py
index 54cee08cefb2..768be3ab7e8c 100644
--- a/lms/djangoapps/lms_xblock/apps.py
+++ b/lms/djangoapps/lms_xblock/apps.py
@@ -22,5 +22,5 @@ def ready(self):
         # monkey-patch the x_module library.
         # TODO: Remove this code when Runtimes are no longer created by modulestores
         # https://openedx.atlassian.net/wiki/display/PLAT/Convert+from+Storage-centric+runtimes+to+Application-centric+runtimes
-        xmodule.x_module.descriptor_global_handler_url = handler_url
-        xmodule.x_module.descriptor_global_local_resource_url = local_resource_url
+        xmodule.x_module.block_global_handler_url = handler_url
+        xmodule.x_module.block_global_local_resource_url = local_resource_url
diff --git a/xmodule/block_metadata_utils.py b/xmodule/block_metadata_utils.py
index b9627568002f..329c53f8c536 100644
--- a/xmodule/block_metadata_utils.py
+++ b/xmodule/block_metadata_utils.py
@@ -34,7 +34,7 @@ def display_name_with_default(block):
     a name based on the URL.
 
     Unlike the rest of this module's functions, this function takes an entire
-    course descriptor/overview as a parameter. This is because a few test cases
+    course block/overview as a parameter. This is because a few test cases
     (specifically, {Text|Image|Video}AnnotationModuleTestCase.test_student_view)
     create scenarios where course.display_name is not None but course.location
     is None, which causes calling course.url_name to fail. So, although we'd
diff --git a/xmodule/conditional_block.py b/xmodule/conditional_block.py
index 5264db255e53..91e7af2c156e 100644
--- a/xmodule/conditional_block.py
+++ b/xmodule/conditional_block.py
@@ -213,8 +213,8 @@ def is_condition_satisfied(self):  # lint-amnesty, pylint: disable=missing-funct
             for block in self.get_required_blocks:
                 if not hasattr(block, attr_name):
                     # We don't throw an exception here because it is possible for
-                    # the descriptor of a required block to have a property but
-                    # for the resulting module to be a (flavor of) ErrorBlock.
+                    # the required block to have a property but
+                    # for the resulting block to be a (flavor of) ErrorBlock.
                     # So just log and return false.
                     if block is not None:
                         # We do not want to log when block is None, and it is when requester
@@ -244,7 +244,7 @@ def student_view(self, _context):
         return fragment
 
     def get_html(self):
-        required_html_ids = [descriptor.location.html_id() for descriptor in self.get_required_blocks]
+        required_html_ids = [block.location.html_id() for block in self.get_required_blocks]
         return self.runtime.service(self, 'mako').render_template('conditional_ajax.html', {
             'element_id': self.location.html_id(),
             'ajax_url': self.ajax_url,
@@ -298,7 +298,7 @@ def get_icon_class(self):
         class_priority = ['video', 'problem']
 
         child_classes = [
-            child_descriptor.get_icon_class() for child_descriptor in self.get_children()
+            child_block.get_icon_class() for child_block in self.get_children()
         ]
         for c in class_priority:
             if c in child_classes:
@@ -318,24 +318,24 @@ def get_required_blocks(self):
         Returns a list of bound XBlocks instances upon which XBlock depends.
         """
         return [
-            self.runtime.get_block_for_descriptor(descriptor) for descriptor in self.get_required_block_descriptors()
+            self.runtime.get_block_for_descriptor(block) for block in self.get_required_block_descriptors()
         ]
 
     def get_required_block_descriptors(self):
         """
         Returns a list of unbound XBlocks instances upon which this XBlock depends.
         """
-        descriptors = []
+        blocks = []
         for location in self.sources_list:
             try:
-                descriptor = self.runtime.get_block(location)
-                descriptors.append(descriptor)
+                block = self.runtime.get_block(location)
+                blocks.append(block)
             except ItemNotFoundError:
                 msg = "Invalid module by location."
                 log.exception(msg)
                 self.runtime.error_tracker(msg)
 
-        return descriptors
+        return blocks
 
     @classmethod
     def definition_from_xml(cls, xml_object, system):
@@ -357,8 +357,8 @@ def definition_from_xml(cls, xml_object, system):
                     show_tag_list.append(location)
             else:
                 try:
-                    descriptor = system.process_xml(etree.tostring(child, encoding='unicode'))
-                    children.append(descriptor.scope_ids.usage_id)
+                    block = system.process_xml(etree.tostring(child, encoding='unicode'))
+                    children.append(block.scope_ids.usage_id)
                 except:  # lint-amnesty, pylint: disable=bare-except
                     msg = "Unable to load child when parsing Conditional."
                     log.exception(msg)
diff --git a/xmodule/error_block.py b/xmodule/error_block.py
index 10a9300bddab..fcebf8f744ff 100644
--- a/xmodule/error_block.py
+++ b/xmodule/error_block.py
@@ -97,8 +97,8 @@ def _construct(cls, system, contents, error_msg, location, for_parent=None):
         if location.block_type == 'error':
             location = location.replace(
                 # Pick a unique url_name -- the sha1 hash of the contents.
-                # NOTE: We could try to pull out the url_name of the errored descriptor,
-                # but url_names aren't guaranteed to be unique between descriptor types,
+                # NOTE: We could try to pull out the url_name of the errored block,
+                # but url_names aren't guaranteed to be unique between block types,
                 # and ErrorBlock can wrap any type.  When the wrapped block is fixed,
                 # it will be written out with the original url_name.
                 name=hashlib.sha1(contents.encode('utf8')).hexdigest()
@@ -141,19 +141,19 @@ def from_json(cls, json_data, system, location, error_msg='Error not available')
         )
 
     @classmethod
-    def from_descriptor(cls, descriptor, error_msg=None):
+    def from_block(cls, block, error_msg=None):
         return cls._construct(
-            descriptor.runtime,
-            str(descriptor),
+            block.runtime,
+            str(block),
             error_msg,
-            location=descriptor.location,
-            for_parent=descriptor.get_parent() if descriptor.has_cached_parent else None
+            location=block.location,
+            for_parent=block.get_parent() if block.has_cached_parent else None
         )
 
     @classmethod
     def from_xml(cls, xml_data, system, id_generator,  # pylint: disable=arguments-differ
                  error_msg=None):
-        '''Create an instance of this descriptor from the supplied data.
+        '''Create an instance of this block from the supplied data.
 
         Does not require that xml_data be parseable--just stores it and exports
         as-is if not.
diff --git a/xmodule/library_content_block.py b/xmodule/library_content_block.py
index e3e38c857017..04abe5de6eb3 100644
--- a/xmodule/library_content_block.py
+++ b/xmodule/library_content_block.py
@@ -468,7 +468,7 @@ def studio_view(self, _context):
         shim_xmodule_js(fragment, self.studio_js_module_name)
         return fragment
 
-    def get_child_descriptors(self):
+    def get_child_blocks(self):
         """
         Return only the subset of our children relevant to the current student.
         """
@@ -701,7 +701,7 @@ def editor_saved(self, user, old_metadata, old_content):  # lint-amnesty, pylint
     def has_dynamic_children(self):
         """
         Inform the runtime that our children vary per-user.
-        See get_child_descriptors() above
+        See get_child_blocks() above
         """
         return True
 
@@ -714,7 +714,7 @@ def get_content_titles(self):
         This overwrites the get_content_titles method included in x_module by default.
         """
         titles = []
-        for child in self.get_child_descriptors():
+        for child in self.get_child_blocks():
             titles.extend(child.get_content_titles())
         return titles
 
diff --git a/xmodule/library_tools.py b/xmodule/library_tools.py
index 5b59cc210d11..58cd8212416f 100644
--- a/xmodule/library_tools.py
+++ b/xmodule/library_tools.py
@@ -125,9 +125,9 @@ def _filter_child(self, usage_key, capa_type):
         if usage_key.block_type != "problem":
             return False
 
-        descriptor = self.store.get_item(usage_key, depth=0)
-        assert isinstance(descriptor, ProblemBlock)
-        return capa_type in descriptor.problem_types
+        block = self.store.get_item(usage_key, depth=0)
+        assert isinstance(block, ProblemBlock)
+        return capa_type in block.problem_types
 
     def can_use_library_content(self, block):
         """
diff --git a/xmodule/randomize_block.py b/xmodule/randomize_block.py
index 6c17804b11bc..c5e1f2c4747f 100644
--- a/xmodule/randomize_block.py
+++ b/xmodule/randomize_block.py
@@ -85,7 +85,7 @@ def child(self):
 
         return child
 
-    def get_child_descriptors(self):
+    def get_child_blocks(self):
         """
         For grading--return just the chosen child.
         """
@@ -99,7 +99,7 @@ def student_view(self, context):
         The student view.
         """
         if self.child is None:
-            # raise error instead?  In fact, could complain on descriptor load...
+            # raise error instead?  In fact, could complain on block load...
             return Fragment(content="<div>Nothing to randomize between</div>")
 
         return self.child.render(STUDENT_VIEW, context)
@@ -120,6 +120,6 @@ def definition_to_xml(self, resource_fs):
     def has_dynamic_children(self):
         """
         Grading needs to know that only one of the children is actually "real".  This
-        makes it use block.get_child_descriptors().
+        makes it use block.get_child_blocks().
         """
         return True
diff --git a/xmodule/services.py b/xmodule/services.py
index c4d00a73906e..595c8082fb5a 100644
--- a/xmodule/services.py
+++ b/xmodule/services.py
@@ -190,7 +190,7 @@ def rebind_noauth_module_to_user(self, block, real_user):
             log.error(err_msg)
             raise RebindUserServiceError(err_msg)
 
-        field_data_cache_real_user = FieldDataCache.cache_for_descriptor_descendents(
+        field_data_cache_real_user = FieldDataCache.cache_for_block_descendents(
             self.course_id,
             real_user,
             block,
diff --git a/xmodule/split_test_block.py b/xmodule/split_test_block.py
index c60d72c863ed..c45848800fb3 100644
--- a/xmodule/split_test_block.py
+++ b/xmodule/split_test_block.py
@@ -177,13 +177,13 @@ class SplitTestBlock(  # lint-amnesty, pylint: disable=abstract-method
     }
 
     @cached_property
-    def child_descriptor(self):
+    def child_block(self):
         """
         Return the child block for the partition or None.
         """
-        child_descriptors = self.get_child_descriptors()
-        if len(child_descriptors) >= 1:
-            return child_descriptors[0]
+        child_blocks = self.get_child_blocks()
+        if len(child_blocks) >= 1:
+            return child_blocks[0]
         return None
 
     @cached_property
@@ -191,15 +191,15 @@ def child(self):
         """
         Return the user bound child block for the partition or None.
         """
-        if self.child_descriptor is not None:
-            return self.runtime.get_block_for_descriptor(self.child_descriptor)
+        if self.child_block is not None:
+            return self.runtime.get_block_for_descriptor(self.child_block)
         else:
             return None
 
-    def get_child_descriptor_by_location(self, location):
+    def get_child_block_by_location(self, location):
         """
         Look through the children and look for one with the given location.
-        Returns the descriptor.
+        Returns the block.
         If none match, return None
         """
         for child in self.get_children():
@@ -227,7 +227,7 @@ def get_content_titles(self):
         """
         return self.child.get_content_titles()
 
-    def get_child_descriptors(self):
+    def get_child_blocks(self):
         """
         For grading--return just the chosen child.
         """
@@ -239,19 +239,19 @@ def get_child_descriptors(self):
         str_group_id = str(group_id)
         if str_group_id in self.group_id_to_child:
             child_location = self.group_id_to_child[str_group_id]
-            child_descriptor = self.get_child_descriptor_by_location(child_location)
+            child_block = self.get_child_block_by_location(child_location)
         else:
             # Oops.  Config error.
             log.debug("configuration error in split test block: invalid group_id %r (not one of %r).  Showing error", str_group_id, list(self.group_id_to_child.keys()))  # lint-amnesty, pylint: disable=line-too-long
 
-        if child_descriptor is None:
-            # Peak confusion is great.  Now that we set child_descriptor,
+        if child_block is None:
+            # Peak confusion is great.  Now that we set child_block,
             # get_children() should return a list with one element--the
             # xmodule for the child
             log.debug("configuration error in split test block: no such child")
             return []
 
-        return [child_descriptor]
+        return [child_block]
 
     def get_group_id(self):
         """
@@ -271,8 +271,8 @@ def _staff_view(self, context):
         inactive_contents = []
 
         for child_location in self.children:  # pylint: disable=no-member
-            child_descriptor = self.get_child_descriptor_by_location(child_location)
-            child = self.runtime.get_block_for_descriptor(child_descriptor)
+            child_block = self.get_child_block_by_location(child_location)
+            child = self.runtime.get_block_for_descriptor(child_block)
             rendered_child = child.render(STUDENT_VIEW, context)
             fragment.add_fragment_resources(rendered_child)
             group_name, updated_group_id = self.get_data_for_vertical(child)
@@ -346,8 +346,8 @@ def studio_render_children(self, fragment, children, context):
         dependencies are added to the specified fragment.
         """
         html = ""
-        for active_child_descriptor in children:
-            active_child = self.runtime.get_block_for_descriptor(active_child_descriptor)
+        for active_child_block in children:
+            active_child = self.runtime.get_block_for_descriptor(active_child_block)
             rendered_child = active_child.render(StudioEditableBlock.get_preview_view_name(active_child), context)
             if active_child.category == 'vertical':
                 group_name, group_id = self.get_data_for_vertical(active_child)
@@ -378,7 +378,7 @@ def student_view(self, context):
         conditions for staff.
         """
         if self.child is None:
-            # raise error instead?  In fact, could complain on descriptor load...
+            # raise error instead?  In fact, could complain on block load...
             return Fragment(content="<div>Nothing here.  Move along.</div>")
 
         if self.runtime.user_is_staff:
@@ -464,8 +464,8 @@ def definition_from_xml(cls, xml_object, system):
 
         for child in xml_object:
             try:
-                descriptor = system.process_xml(etree.tostring(child))
-                children.append(descriptor.scope_ids.usage_id)
+                block = system.process_xml(etree.tostring(child))
+                children.append(block.scope_ids.usage_id)
             except Exception:  # lint-amnesty, pylint: disable=broad-except
                 msg = "Unable to load child when parsing split_test block."
                 log.exception(msg)
@@ -486,7 +486,7 @@ def get_context(self):
     def has_dynamic_children(self):
         """
         Grading needs to know that only one of the children is actually "real".  This
-        makes it use block.get_child_descriptors().
+        makes it use block.get_child_blocks().
         """
         return True
 
@@ -561,9 +561,9 @@ def active_and_inactive_children(self):
         if not user_partition:
             return [], children
 
-        def get_child_descriptor(location):
+        def get_child_block(location):
             """
-            Returns the child descriptor which matches the specified location, or None if one is not found.
+            Returns the child block which matches the specified location, or None if one is not found.
             """
             for child in children:
                 if child.location == location:
@@ -575,7 +575,7 @@ def get_child_descriptor(location):
         for group in user_partition.groups:
             group_id = str(group.id)
             child_location = self.group_id_to_child.get(group_id, None)
-            child = get_child_descriptor(child_location)
+            child = get_child_block(child_location)
             if child:
                 active_children.append(child)
 
diff --git a/xmodule/studio_editable.py b/xmodule/studio_editable.py
index 2795bf31bca8..844f0f446c37 100644
--- a/xmodule/studio_editable.py
+++ b/xmodule/studio_editable.py
@@ -51,8 +51,8 @@ def get_preview_view_name(block):
         return AUTHOR_VIEW if has_author_view(block) else STUDENT_VIEW
 
 
-def has_author_view(descriptor):
+def has_author_view(block):
     """
-    Returns True if the xmodule linked to the descriptor supports "author_view".
+    Returns True if the xmodule linked to the block supports "author_view".
     """
-    return getattr(descriptor, 'has_author_view', False)
+    return getattr(block, 'has_author_view', False)
diff --git a/xmodule/templates.py b/xmodule/templates.py
index f019d5ee409e..550d84ae4391 100644
--- a/xmodule/templates.py
+++ b/xmodule/templates.py
@@ -21,13 +21,13 @@
 
 def all_templates():
     """
-    Returns all templates for enabled modules, grouped by descriptor type
+    Returns all templates for enabled modules, grouped by block type
     """
     # TODO use memcache to memoize w/ expiration
     templates = defaultdict(list)
-    for category, descriptor in XBlock.load_classes():
-        if not hasattr(descriptor, 'templates'):
+    for category, block in XBlock.load_classes():
+        if not hasattr(block, 'templates'):
             continue
-        templates[category] = descriptor.templates()
+        templates[category] = block.templates()
 
     return templates
diff --git a/xmodule/video_block/transcripts_utils.py b/xmodule/video_block/transcripts_utils.py
index 0cbc79945b8d..39f18ca741ca 100644
--- a/xmodule/video_block/transcripts_utils.py
+++ b/xmodule/video_block/transcripts_utils.py
@@ -241,13 +241,13 @@ def get_transcripts_from_youtube(youtube_id, settings, i18n, youtube_transcript_
     return {'start': sub_starts, 'end': sub_ends, 'text': sub_texts}
 
 
-def download_youtube_subs(youtube_id, video_descriptor, settings):  # lint-amnesty, pylint: disable=redefined-outer-name
+def download_youtube_subs(youtube_id, video_block, settings):  # lint-amnesty, pylint: disable=redefined-outer-name
     """
     Download transcripts from Youtube.
 
     Args:
         youtube_id: str, actual youtube_id of the video.
-        video_descriptor: video descriptor instance.
+        video_block: video block instance.
 
     We save transcripts for 1.0 speed, as for other speed conversion is done on front-end.
 
@@ -257,7 +257,7 @@ def download_youtube_subs(youtube_id, video_descriptor, settings):  # lint-amnes
     Raises:
         GetTranscriptsFromYouTubeException, if fails.
     """
-    i18n = video_descriptor.runtime.service(video_descriptor, "i18n")
+    i18n = video_block.runtime.service(video_block, "i18n")
     _ = i18n.ugettext
 
     subs = get_transcripts_from_youtube(youtube_id, settings, i18n)
@@ -961,7 +961,7 @@ def get_transcript_from_contentstore(video, language, output_format, transcripts
     Get video transcript from content store.
 
     Arguments:
-        video (Video Descriptor): Video descriptor
+        video (Video block): Video block
         language (unicode): transcript language
         output_format (unicode): transcript output format
         transcripts_info (dict): transcript info for a video
@@ -1089,7 +1089,7 @@ def get_transcript(video, lang=None, output_format=Transcript.SRT, youtube_id=No
     Get video transcript from edx-val or content store.
 
     Arguments:
-        video (Video Descriptor): Video Descriptor
+        video (Video block): Video block
         lang (unicode): transcript language
         output_format (unicode): transcript output format
         youtube_id (unicode): youtube video id
diff --git a/xmodule/x_module.py b/xmodule/x_module.py
index 031a895b0faa..3434a80b3955 100644
--- a/xmodule/x_module.py
+++ b/xmodule/x_module.py
@@ -286,7 +286,7 @@ class XModuleMixin(XModuleFields, XBlock):
 
     Adding this Mixin to an :class:`XBlock` allows it to cooperate with old-style :class:`XModules`
     """
-    # Attributes for inspection of the descriptor
+    # Attributes for inspection of the block
 
     # This indicates whether the xmodule is a problem-type.
     # It should respond to max_score() and grade(). It can be graded or ungraded
@@ -299,7 +299,7 @@ class XModuleMixin(XModuleFields, XBlock):
 
     # Class level variable
 
-    # True if this descriptor always requires recalculation of grades, for
+    # True if this block always requires recalculation of grades, for
     # example if the score can change via an extrnal service, not just when the
     # student interacts with the module on the page.  A specific example is
     # FoldIt, which posts grade-changing updates through a separate API.
@@ -563,10 +563,10 @@ def get_icon_class(self):
 
     def has_dynamic_children(self):
         """
-        Returns True if this descriptor has dynamic children for a given
+        Returns True if this block has dynamic children for a given
         student when the module is created.
 
-        Returns False if the children of this descriptor are the same
+        Returns False if the children of this block are the same
         children that the module will return for any student.
         """
         return False
@@ -1002,7 +1002,7 @@ def wrap_aside(self, block, aside, view, frag, context):    # pylint: disable=un
 # Runtime.handler_url interface.
 #
 # The monkey-patching happens in cms/djangoapps/xblock_config/apps.py and lms/djangoapps/lms_xblock/apps.py
-def descriptor_global_handler_url(block, handler_name, suffix='', query='', thirdparty=False):
+def block_global_handler_url(block, handler_name, suffix='', query='', thirdparty=False):
     """
     See :meth:`xblock.runtime.Runtime.handler_url`.
     """
@@ -1014,7 +1014,7 @@ def descriptor_global_handler_url(block, handler_name, suffix='', query='', thir
 # the Runtime part of its interface. This function matches the Runtime.local_resource_url interface
 #
 # The monkey-patching happens in cms/djangoapps/xblock_config/apps.py and lms/djangoapps/lms_xblock/apps.py
-def descriptor_global_local_resource_url(block, uri):
+def block_global_local_resource_url(block, uri):
     """
     See :meth:`xblock.runtime.Runtime.local_resource_url`.
     """
@@ -1529,7 +1529,7 @@ def handler_url(self, block, handler_name, suffix='', query='', thirdparty=False
         # defined for LMS/CMS through the handler_url_override property.
         if getattr(self, 'handler_url_override', None):
             return self.handler_url_override(block, handler_name, suffix, query, thirdparty)
-        return descriptor_global_handler_url(block, handler_name, suffix, query, thirdparty)
+        return block_global_handler_url(block, handler_name, suffix, query, thirdparty)
 
     def local_resource_url(self, block, uri):
         """
@@ -1539,7 +1539,7 @@ def local_resource_url(self, block, uri):
         # This means that LMS/CMS don't have a way to define a subclass of DescriptorSystem
         # that implements the correct local_resource_url. So, for now, instead, we will reference a
         # global function that the application can override.
-        return descriptor_global_local_resource_url(block, uri)
+        return block_global_local_resource_url(block, uri)
 
     def applicable_aside_types(self, block):
         """
diff --git a/xmodule/xml_block.py b/xmodule/xml_block.py
index e67e23604635..cb7c096ce942 100644
--- a/xmodule/xml_block.py
+++ b/xmodule/xml_block.py
@@ -152,7 +152,7 @@ def _get_metadata_from_xml(xml_object, remove=True):
     @classmethod
     def definition_from_xml(cls, xml_object, system):
         """
-        Return the definition to be passed to the newly created descriptor
+        Return the definition to be passed to the newly created block
         during from_xml
 
         xml_object: An etree Element
@@ -199,7 +199,7 @@ def load_file(cls, filepath, fs, def_id):  # pylint: disable=invalid-name
     @classmethod
     def load_definition(cls, xml_object, system, def_id, id_generator):
         """
-        Load a descriptor definition from the specified xml_object.
+        Load a block from the specified xml_object.
         Subclasses should not need to override this except in special
         cases (e.g. html block)
 
@@ -365,7 +365,7 @@ def parse_xml(cls, node, runtime, _keys, id_generator):
 
         xblock = runtime.construct_xblock_from_class(
             cls,
-            # We're loading a descriptor, so student_id is meaningless
+            # We're loading a block, so student_id is meaningless
             ScopeIds(None, node.tag, def_id, usage_id),
             field_data,
         )
@@ -405,7 +405,7 @@ def _format_filepath(cls, category, name):
         return f'{category}/{name}.{cls.filename_extension}'
 
     def export_to_file(self):
-        """If this returns True, write the definition of this descriptor to a separate
+        """If this returns True, write the definition of this block to a separate
         file.
 
         NOTE: Do not override this without a good reason.  It is here