    def reorder_incremental_state(
        self, incremental_state: Dict[str, Dict[str, Optional[Tensor]]], new_order
    ):
        """Reorder buffered internal state (for incremental generation)."""
        input_buffer = self._get_input_buffer(incremental_state)
        if input_buffer is not None:
            for k in input_buffer.keys():
                if input_buffer[k] is not None:
                    input_buffer[k] = input_buffer[k].index_select(0, new_order)
            incremental_state = self._set_input_buffer(incremental_state, input_buffer)
        return incremental_state
Reorder buffered internal state (for incremental generation).
fairseq/model_parallel/modules/multihead_attention.py