def METHOD_NAME(self, batch_size=1) -> InputSpec:
    return InputSpec(
        {
            "past_target": Input(
                shape=(batch_size, self._past_length), dtype=torch.float
            ),
            "past_observed_values": Input(
                shape=(batch_size, self._past_length), dtype=torch.float
            ),
        },
        torch.zeros,
    )