def _validator_args_logic(args):
    """
    Implements logic for how validator arguments work in combination.

    As per: https://github.com/XLSForm/pyxform/pull/167#issuecomment-353382008

    **backwards-compatible**
    `xls2xform.py myform --skip_validate`: no validators
    `xls2xform.py myform`: ODK only

    **new**
    `xls2xform.py myform --enketo_validate`: Enketo only
    `xls2xform.py myform --odk_validate`: ODK only
    `xls2xform.py myform --enketo_validate --odk_validate`: both
    `xls2xform.py myform --enketo_validate --odk_validate --skip_validate`: no validators
    """
    if not args.skip_validate:
        args.odk_validate = False
        args.enketo_validate = False
    elif args.skip_validate and not (args.odk_validate or args.enketo_validate):
        args.odk_validate = True
        args.enketo_validate = False
    return args