code: def add_custom_options(parser):
      
      parser.add_argument("--outliers-of", type=str, metavar="POP",
                          default="CEU", choices=["CEU", "YRI", "JPT-CHB"],
                          help=("Finds the outliers of this population. "
                                "[default: %(default)s]"))
      parser.add_argument("--multiplier", type=float, metavar="FLOAT",
                          default=1.9,
                          help=("To find the outliers, we look for more than "
                                "x times the cluster standard deviation. "
                                "[default: %(default).1f]"))
      parser.add_argument("--xaxis", type=str, metavar="COMPONENT", default="C1",
                          choices=["C{}".format(i) for i in xrange(1, 11)],
                          help=("The component to use for the X axis. "
                                "[default: %(default)s]"))
      parser.add_argument("--yaxis", type=str, metavar="COMPONENT", default="C2",
                          choices=["C{}".format(i) for i in xrange(1, 11)],
                          help=("The component to use for the Y axis. "
                                "[default: %(default)s]"))
docs: Adds custom options to a parser.
  
      :param parser: the parser to which to add options.
  
      :type parser: argparse.ArgumentParser