def _add_include_arg(arg_parser):
    """
    Adds optional repeatable include parameter to a parser.
    :param arg_parser: ArgumentParser parser to add this argument to.
    """
    arg_parser.add_argument("--include",
                            metavar='Path',
                            action='append',
                            type=to_unicode,
                            dest='include_paths',
                            help="Specifies a single path to include. This argument can be repeated.",
                            default=[])