function Load$1(params) {
    Transform.call(this, [], params);
    this._pending = null;
  }
Load and parse data from an external source. Marshalls parameter
values and then invokes the Dataflow request method.
@constructor
@param {object} params - The parameters for this operator.
@param {string} params.url - The URL to load from.
@param {object} params.format - The data format options.