Extra comments explaining that we use requested annotations' type

instead of topic_type if pub_as_list is false.

srv/PubAnnotationsData.srv

@@ -1,6 +1,9 @@
 # Request server to publish annotations' data for a list of annotation identifiers
 # If pub_as_list is true, annotations will be packed in a list before publishing,
-# so topic_type must be an array of the requested annotations
+# so topic_type must be an array of the requested annotations. However, if is false,
+# topic_type is just ignored and the published topic type is obtained from one of
+# the annotations in the list
+# NOTE: in both cases, all annotations must be of the same type
 
 uuid_msgs/UniqueID[] annotation_ids
 string topic_name