@classmethod
def docker(klass, container_id, shell, script, interval, deregister=None):
    """
        Invoke *script* packaged within a running docker container with
        *container_id* at a specified *interval* on the configured
        *shell* using the Docker Exec API.  Optional *register* after which a
        failing service will be automatically deregistered.
        """
    ret = {'docker_container_id': container_id, 'shell': shell, 'script':
        script, 'interval': interval}
    if deregister:
        ret['DeregisterCriticalServiceAfter'] = deregister
    return ret
