Adjustments based on code review feedback

image/docker/schema2/list.py

@@ -183,10 +183,14 @@ class DockerSchema2ManifestList(ManifestInterface):
     except ValidationError as ve:
       raise MalformedSchema2ManifestList('manifest data does not match schema: %s' % ve)
 
+  @property
+  def is_manifest_list(self):
+    """ Returns whether this manifest is a list. """
+    return True
+
   @property
   def schema_version(self):
-    """ The version of the schema, or None for lists. """
-    return None
+    return 2
 
   @property
   def digest(self):