<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def generic_converter_cli(docgraph_class, file_descriptor=''):
 """ generic command line interface for importers. Will convert the file specified on the command line into a dot representation of the corresponding DiscourseDocumentGraph and write the output to stdout or a file specified on the command line. Parameters docgraph_class : class a DiscourseDocumentGraph (or a class derived from it), not an instance of it! file_descriptor : str string descring the input format, e.g. 'TigerXML (syntax)' """

    parser = argparse.ArgumentParser()
    parser.add_argument('input_file',
                        help='{} file to be converted'.format(file_descriptor))
    parser.add_argument('output_file', nargs='?', default=sys.stdout)
    args = parser.parse_args(sys.argv[1:])

    assert os.path.isfile(args.input_file), \
        "'{}' isn't a file".format(args.input_file)
    docgraph = docgraph_class(args.input_file)
    write_dot(docgraph, args.output_file)