def get_main_app_sub_parser(parent_parser):
    """
    Creates and adds a sub_parser to parent_parser.
    Returns the sub_parser

    :param parent_parser: Parser to add the sub_parser to
    :type parent_parser: argparse.ArgumentParser
    :return: Sub Parser
    :rtype: argparse.ArgumentParser
    """
    # Define sub_parser object, its dest is cmd
    sub_parser = parent_parser.add_subparsers(
        title="subcommands",
        description="one of these subcommands must be provided",
        metavar="",
        dest="cmd"
    )

    return sub_parser