def __delitem__(self, query_filter):
    subquery_count = len(self.__bound_queries)
    keyerror_count = 0
    saved_items = []
    for index, query in enumerate(self.__bound_queries):
      try:
        saved_items.append(query.get(query_filter, None))
        del query[query_filter]
      except KeyError:
        keyerror_count += 1
      except:
        for q, old_value in itertools.izip(self.__bound_queries[:index],
                                           saved_items):
          if old_value is not None:
            q[query_filter] = old_value
        raise

    if keyerror_count == subquery_count:
      raise KeyError(query_filter)
Delete a filter by deleting it from all subqueries.
dataset/ETHPy150Open CollabQ/CollabQ/.google_appengine/google/appengine/api/datastore.py/MultiQuery.__delitem__