src/transformers/models/gpt2/configuration_gpt2.py/GPT2OnnxConfig/outputs
class GPT2OnnxConfig:    def outputs(self) -> Mapping[str, Mapping[int, str]]:
        common_outputs = OrderedDict({"last_hidden_state": {0: "batch", 1: "sequence"}})
        if self.use_past:
            for i in range(self._config.n_layer * 2):
                common_outputs[f"present.{i}"] = {0: "batch", 2: "sequence"}

            return common_outputs

        return common_outputs