    def reduce_metrics(cls, logging_outputs: List[Dict[str, Any]]) -> None:
        """Aggregate logging outputs from data parallel training."""
        utils.deprecation_warning(
            "Criterions should implement the reduce_metrics API. "
            "Falling back to deprecated aggregate_logging_outputs API."
        )
        agg_logging_outputs = cls.aggregate_logging_outputs(logging_outputs)
        for k, v in agg_logging_outputs.items():
            if k in {"nsentences", "ntokens", "sample_size"}:
                continue
            metrics.log_scalar(k, v)
Aggregate logging outputs from data parallel training.
fairseq/criterions/fairseq_criterion.py