def dataset(self, split):
        """
        Return a loaded dataset split.

        Args:
            split (str): name of the split (e.g., train, valid, test)

        Returns:
            a :class:`~fairseq.data.FairseqDataset` corresponding to *split*
        """
        from fairseq.data import FairseqDataset

        if split not in self.datasets:
            raise KeyError("Dataset not loaded: " + split)
        if not isinstance(self.datasets[split], FairseqDataset):
            raise TypeError("Datasets are expected to be of type FairseqDataset")
        return self.datasets[split]

        Return a loaded dataset split.

        Args:
            split (str): name of the split (e.g., train, valid, test)

        Returns:
            a :class:`~fairseq.data.FairseqDataset` corresponding to *split*
        
understand_icl/fairseq/fairseq/tasks/fairseq_task.py