def add_output_compression_type(parser):
    """Add compression arguments to a parser object."""
    group = parser.add_mutually_exclusive_group()
    group.add_argument('--gzip', default=False, action='store_true', help=
        'Compress output using gzip')
    group.add_argument('--bzip', default=False, action='store_true', help=
        'Compress output using bzip2')
