'Construct a query for this key range, including the scan direction.
Args:
kind_class: A kind implementation class (a subclass of either
db.Model or ndb.Model).
keys_only: bool, default False, use keys_only on Query?
Returns:
A db.Query or ndb.Query instance (corresponding to kind_class).
Raises:
KeyRangeError: if self.direction is not in (KeyRange.ASC, KeyRange.DESC).'

def make_directed_query(self, kind_class, keys_only=False):

    if (ndb is not None):
        if issubclass(kind_class, ndb.Model):
            return self.make_directed_ndb_query(kind_class, keys_only=keys_only)
    assert (self._app is None), '_app    is    not    supported    for    db.Query'
    direction = self.__get_direction('', '-')
    query = db.Query(kind_class, namespace=self.namespace, keys_only=keys_only)
    query.order(('%s__key__' % direction))
    query = self.filter_query(query)
    return query
