code: function constructor(service, state) {
      this.service = service;
      this.state = state;
  
      if (typeof this.state === 'object') {
        AWS.util.each.call(this, this.state, function (key, value) {
          this.state = key;
          this.expectedValue = value;
        });
      }
  
      this.loadWaiterConfig(this.state);
      if (!this.expectedValue) {
        this.expectedValue = this.config.successValue;
      }
    }
docs: Waits for a given state on a service object
  @param service [Service] the service object to wait on
  @param state [String] the state (defined in waiter configuration) to wait
  for.
  @example Create a waiter for running EC2 instances
  var ec2 = new AWS.EC2;
  var waiter = new AWS.ResourceWaiter(ec2, 'instanceRunning');