def override_module_args(args: Namespace) -> Tuple[List[str], List[str]]:
    """use the field in args to overrides those in cfg"""
    overrides = []
    deletes = []

    for k in FairseqConfig.__dataclass_fields__.keys():
        overrides.extend(
            _override_attr(k, FairseqConfig.__dataclass_fields__[k].type, args)
        )

    if args is not None:
        if hasattr(args, "task"):
            from fairseq.tasks import TASK_DATACLASS_REGISTRY

            migrate_registry(
                "task", args.task, TASK_DATACLASS_REGISTRY, args, overrides, deletes
            )
        else:
            deletes.append("task")

        # these options will be set to "None" if they have not yet been migrated
        # so we can populate them with the entire flat args
        CORE_REGISTRIES = {"criterion", "optimizer", "lr_scheduler"}

        from fairseq.registry import REGISTRIES

        for k, v in REGISTRIES.items():
            if hasattr(args, k):
                migrate_registry(
                    k,
                    getattr(args, k),
                    v["dataclass_registry"],
                    args,
                    overrides,
                    deletes,
                    use_name_as_val=k not in CORE_REGISTRIES,
                )
            else:
                deletes.append(k)

        no_dc = True
        if hasattr(args, "arch"):
            from fairseq.models import ARCH_MODEL_REGISTRY, ARCH_MODEL_NAME_REGISTRY

            if args.arch in ARCH_MODEL_REGISTRY:
                m_cls = ARCH_MODEL_REGISTRY[args.arch]
                dc = getattr(m_cls, "__dataclass", None)
                if dc is not None:
                    m_name = ARCH_MODEL_NAME_REGISTRY[args.arch]
                    overrides.append("model={}".format(m_name))
                    overrides.append("model._name={}".format(args.arch))
                    # override model params with those exist in args
                    overrides.extend(_override_attr("model", dc, args))
                    no_dc = False
        if no_dc:
            deletes.append("model")

    return overrides, deletes
use the field in args to overrides those in cfg
fairseq/dataclass/utils.py