def add_subtools(o):
    """Add subtools to the given parser."""
    o = o.add_argument_group('subtools')
    o.add_argument('--generate-builtins', action='store', dest=
        'generate_builtins', default=None, help=
        'Precompile builtins pyi and write to the given file.')
    o.add_argument('--parse-pyi', action='store_true', dest='parse_pyi',
        default=False, help='Try parsing a PYI file. For testing of typeshed.')
