code: def do_bulk_config_update(hostnames):
    
    api = ApiResource(CM_HOST, username=CM_USER, password=CM_PASSWD)
    hosts = collect_hosts(api, hostnames)
  
    # Set config
    for h in hosts:
      configure_roles_on_host(api, h)
docs: Given a list of hostnames, update the configs of all the
    datanodes, tasktrackers and regionservers on those hosts.