def METHOD_NAME(opt, parser):
    """Parses the CLI options, verifies that they are consistent and
    reasonable, and acts on them if they are
    Parameters
    ----------
    opt : object
        Result of parsing the CLI with OptionParser, or any object with the
        required attributes
    parser : object
        OptionParser instance.
    """
    # Pin to specified CPUs if requested
    requested_cpus = None
    if opt.cpu_affinity_from_env is not None:
        if opt.cpu_affinity is not None:
            logging.error("Both --cpu_affinity_from_env and --cpu_affinity specified")
            sys.exit(1)
        requested_cpus = os.environ.get(opt.cpu_affinity_from_env)
        if requested_cpus is None:
            logging.error("CPU affinity requested from environment variable %s "
                          "but this variable is not defined" % opt.cpu_affinity_from_env)
            sys.exit(1)
        if requested_cpus == '':
            logging.error("CPU affinity requested from environment variable %s "
                          "but this variable is empty" % opt.cpu_affinity_from_env)
            sys.exit(1)
    if requested_cpus is None:
        requested_cpus = opt.cpu_affinity
    if requested_cpus is not None:
        command = 'taskset -pc %s %d' % (requested_cpus, os.getpid())
        retcode = os.system(command)
        if retcode != 0:
            logging.error('taskset command <%s> failed with return code %d' % \
                          (command, retcode))
            sys.exit(1)
        logging.info("Pinned to CPUs %s " % requested_cpus)