def __delitem__(self, query_filter):
    """Delete a filter by deleting it from all subqueries.

    If a KeyError is raised during the attempt, it is ignored, unless
    every subquery raised a KeyError. If any other exception is
    raised, any deletes will be rolled back.

    Args:
      query_filter: the filter to delete.

    Raises:
      KeyError: No subquery had an entry containing 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 __HOLE__:
        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)
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/api/datastore.py/MultiQuery.__delitem__