def subparser(subparsers):
    """Define the `kevlar mutate` command-line interface."""
    desc = 'Apply the specified mutations to the genome provided.'
    subparser = subparsers.add_parser('mutate', description=desc)
    subparser.add_argument('-o', '--out', metavar='FILE', help=
        'output file; default is terminal (stdout)')
    subparser.add_argument('mutations', help='mutations file')
    subparser.add_argument('genome', help='genome to mutate')
