code: def from_legacy_urlsafe(cls, urlsafe):
          
          urlsafe = _to_bytes(urlsafe, encoding="ascii")
          padding = b"=" * (-len(urlsafe) % 4)
          urlsafe += padding
          raw_bytes = base64.urlsafe_b64decode(urlsafe)
  
          reference = _app_engine_key_pb2.Reference()
          reference.ParseFromString(raw_bytes)
  
          project = _clean_app(reference.app)
          namespace = _get_empty(reference.name_space, u"")
          _check_database_id(reference.database_id)
          flat_path = _get_flat_path(reference.path)
          return cls(*flat_path, project=project, namespace=namespace)
docs: Convert urlsafe string to :class:`~google.cloud.datastore.key.Key`.
  
          This is intended to work with the "legacy" representation of a
          datastore "Key" used within Google App Engine (a so-called
          "Reference"). This assumes that ``urlsafe`` was created within an App
          Engine app via something like ``ndb.Key(...).urlsafe()``.
  
          :type urlsafe: bytes or unicode
          :param urlsafe: The base64 encoded (ASCII) string corresponding to a
                          datastore "Key" / "Reference".
  
          :rtype: :class:`~google.cloud.datastore.key.Key`.
          :returns: The key corresponding to ``urlsafe``.