@staticmethod
def setup_command_line(parser):
    """Setup the command line options for pigeonhole principle formula

        Arguments:
        - `parser`: parser to load with options.
        """
    parser.add_argument('pigeons', metavar='<pigeons>', type=int, help=
        'Number of pigeons')
    parser.add_argument('holes', metavar='<holes>', type=int, help=
        'Number of holes')
    parser.add_argument('--functional', action='store_true', help=
        'pigeons sit in at most one hole')
    parser.add_argument('--onto', action='store_true', help=
        'every hole has a sitting pigeon')
