Define a hash method in the same way as Base.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@669 20353a03-c40f-0410-a6d1-a30d3c3de9de

product/ERP5Type/XMLObject.py

@@ -79,5 +79,9 @@ class XMLObject( Folder ):
       """
       pass
 
+    # Hash method
+    def __hash__(self):
+      return self.getUid()
+
 
 InitializeClass(XMLObject)