gistfile1.txt

def prefetch_refprops(entities, *props):
    fields = [(entity, prop) for entity in entities for prop in props]
    ref_keys = set(prop.get_value_for_datastore(x) for x, prop in fields)
    ref_keys.discard(None)
    ref_entities = dict((x.key(), x) for x in db.get(ref_keys))
    for (entity, prop), ref_key in zip(fields, ref_keys):
        prop.__set__(entity, ref_entities[ref_key])
    return entities