code: function makeUnauthenticatedRequest(operation, params, callback) {
      if (typeof params === 'function') {
        callback = params;
        params = {};
      }
  
      var request = this.makeRequest(operation, params).toUnauthenticated();
      return callback ? request.send(callback) : request;
    }
docs: Calls an operation on a service with the given input parameters, without
  any authentication data. This method is useful for "public" API operations.
  
  @param operation [String] the name of the operation to call on the service.
  @param params [map] a map of input options for the operation
  @callback callback function(err, data)
  If a callback is supplied, it is called when a response is returned
  from the service.
  @param err [Error] the error object returned from the request.
  Set to `null` if the request is successful.
  @param data [Object] the de-serialized data returned from
  the request. Set to `null` if a request error occurs.