    def add_args(parser):
        """Add task-specific arguments to the parser."""
        parser.add_argument(
            "data",
            help="colon separated path to data directories list, \
                            will be iterated upon during epochs in round-robin manner",
        )
        parser.add_argument(
            "--tokens-per-sample",
            default=512,
            type=int,
            help="max number of total tokens over all segments"
            " per sample for BERT dataset",
        )
        parser.add_argument(
            "--break-mode", default="doc", type=str, help="mode for breaking sentence"
        )
        parser.add_argument("--shuffle-dataset", action="store_true", default=False)
Add task-specific arguments to the parser.
fairseq/tasks/legacy_masked_lm.py