'Create a copy of the source and mark its revision as draft.
Note: This method is to support the Mongo Modulestore and may be deprecated.
:param location: the location of the source (its revision must be None)'

def convert_to_draft(self, location, user_id):

    store = self._verify_modulestore_support(location.course_key, 'convert_to_draft')
    return store.convert_to_draft(location, user_id)
