def add_reductions(parser):
    """Add reduction options to a parser"""
    reductions = parser.add_mutually_exclusive_group()
    reductions.add_argument('--dpr', metavar='<role:count,role:count,...>',
        help="""Specify a
        deviation preserving reduction.""")
    reductions.add_argument('--hr', metavar='<role:count,role:count,...>',
        help="""Specify a
        hierarchical reduction.""")
