src/transformers/onnx/config.py/OnnxSeq2SeqConfigWithPast/_flatten_past_key_values_
class OnnxSeq2SeqConfigWithPast:    def _flatten_past_key_values_(self, flattened_output, name, idx, t):
        flattened_output[f"{name}.{idx}.decoder.key"] = t[0]
        flattened_output[f"{name}.{idx}.decoder.value"] = t[1]
        flattened_output[f"{name}.{idx}.encoder.key"] = t[2]
        flattened_output[f"{name}.{idx}.encoder.value"] = t[3]