run_mlm_no_trainer.py requires --model_name_or_path
The `examples/pytorch/language-modeling/run_mlm_no_trainer.py` script has

    parser.add_argument(
        "--model_name_or_path",
        type=str,
        help="Path to pretrained model or model identifier from huggingface.co/models.",
        default=None,
        required=True,
    )

Despite there being several checks in the code implying it may be None ie

    if args.model_name_or_path:
        model = AutoModelForMaskedLM.from_pretrained(
            args.model_name_or_path,
            from_tf=bool(".ckpt" in args.model_name_or_path),
            config=config,
        )
    else:
        logger.info("Training new model from scratch")
        model = AutoModelForMaskedLM.from_config(config)

As far as I can see it's optional, falling back to training a new model from scratch - just like run_mlm.py (I commented out `required=True` without any obvious issues).

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