Remove repeated code

src/github/Repository.py

@@ -2,6 +2,7 @@
 # Do not modify it manually, your work would be lost.
 
 import PaginatedList
+from GithubObject import *
 import Branch
 import IssueEvent
 import Label
@@ -25,11 +26,6 @@ import Tag
 import GitTag
 import Download
 import Event
-# This allows None as a valid value for an optional parameter
-
-class DefaultValueForOptionalParametersType:
-    pass
-DefaultValueForOptionalParameters = DefaultValueForOptionalParametersType()
 
 class Repository( object ):
     def __init__( self, requester, attributes, lazy ):