Adds custom options to a parser.

    :param parser: the parser.

    :type parser: argparse.parser

def addCustomOptions(parser):
    """Adds custom options to a parser.

    :param parser: the parser.

    :type parser: argparse.parser

    """
    parser.add_argument("--format", type=str, metavar="FORMAT", default="png",
                        choices=["png", "ps", "pdf", "X11"],
                        help="The output file format (png, ps, pdf, or X11 "
                             "formats are available). [default: %(default)s]")
    parser.add_argument("--title", type=str, metavar="STRING",
                        default="C2 in function of C1 - MDS",
                        help="The title of the MDS plot. [default: "
                             "%(default)s]")
    parser.add_argument("--xlabel", type=str, metavar="STRING", default="C1",
                        help="The label of the X axis. [default: %(default)s]")
    parser.add_argument("--ylabel", type=str, metavar="STRING", default="C2",
                        help="The label of the Y axis. [default: %(default)s]")