def obtainChoicesKey( self, field ):
'''This method returns a key that can be used by the client to cache the
value returned by choices(). If the client already has the key cached on
the client side, it can provide the choice list from its cache rather than
calling choices() on this object again.
If there is no caching key, this method will return null.
'''
if field.getID() == self.MEMBERS_FIELD_ID:
return None
else:
return BaseJythonEditObject.obtainChoicesKey( self, field )
