minor fix in ImageField docstring

mongoengine/fields.py

@@ -1867,12 +1867,9 @@ class ImageField(FileField):
     """
     A Image File storage field.
 
-    @size (width, height, force):
-        max size to store images, if larger will be automatically resized
-        ex: size=(800, 600, True)
-
-    @thumbnail (width, height, force):
-        size to generate a thumbnail
+    :param size: max size to store images, provided as (width, height, force)
+        if larger, it will be automatically resized (ex: size=(800, 600, True))
+    :param thumbnail_size: size to generate a thumbnail, provided as (width, height, force)
 
     .. versionadded:: 0.6
     """

tests/fields/fields.py

@@ -618,6 +618,8 @@ class Person(Document):
         self.assertRaises(ValidationError, person.validate)
         person.admin = 'Yes'
         self.assertRaises(ValidationError, person.validate)
+        person.admin = 'False'
+        self.assertRaises(ValidationError, person.validate)
 
     def test_uuid_field_string(self):
         """Test UUID fields storing as String
@@ -2905,7 +2907,6 @@ class Attachment(Document):
         for invalid_data in (2, u'Im_a_unicode', ['some_str']):
             self.assertRaises(ValidationError, Attachment(blob=invalid_data).validate)
 
-
     def test_binary_field_primary(self):
         class Attachment(Document):
             id = BinaryField(primary_key=True)