The wire format is an AnyValue message.

def ConvertFromWireFormat(self, value, container=None):
    """The wire format is an AnyValue message."""
    result = AnyValue()
    ReadIntoObject(value[2], 0, result)
    if self._type is not None:
      converted_value = self._type(container)
    else:
      converted_value = self._TypeFromAnyValue(result)

    # If one of the protobuf library wrapper classes is used, unwrap the value.
    if result.type_url.startswith("type.googleapis.com/google.protobuf."):
      wrapper_cls = self.__class__.WRAPPER_BY_TYPE[
          converted_value.data_store_type]
      wrapper_value = wrapper_cls()
      wrapper_value.ParseFromString(result.value)
      return converted_value.FromDatastoreValue(wrapper_value.value)
    else:
      # TODO(user): Type stored in type_url is currently ignored when value
      # is decoded. We should use it to deserialize the value and then check
      # that value type and dynamic type are compatible.
      return converted_value.FromSerializedString(result.value)