How to use the johnnydep.__doc__ function in johnnydep

def main():
    default_fields = os.environ.get("JOHNNYDEP_FIELDS", "name,summary").split(",")
    parser = ArgumentParser(description=johnnydep.__doc__)
    parser.add_argument("req", help="The project name or requirement specifier")
    parser.add_argument("--index-url", "-i")
    parser.add_argument("--extra-index-url")
    parser.add_argument(
        "--output-format",
        "-o",
        choices=["human", "json", "yaml", "python", "toml", "pinned"],
        default="human",
    )
    parser.add_argument(
        "--no-deps", help="Don't recurse the dependency tree", dest="recurse", action="store_false"
    )
    parser.add_argument(
        "--fields", "-f", nargs="*", default=default_fields, choices=list(FIELDS) + ["ALL"]
    )
    parser.add_argument("--for-python", "-p", dest="env", type=python_interpreter)