'Converts a list of v3 References to a list of v1 Keys.
Args:
v3_refs: a list of entity_pb.Reference objects
Returns:
a list of googledatastore.Key objects'

def v3_to_v1_keys(self, v3_refs):

    v1_keys = []
    for v3_ref in v3_refs:
        v1_key = googledatastore.Key()
        self.v3_to_v1_key(v3_ref, v1_key)
        v1_keys.append(v1_key)
    return v1_keys
