code: function FormData(options) {
    if (!(this instanceof FormData)) {
      return new FormData();
    }
  
    this._overheadLength = 0;
    this._valueLength = 0;
    this._valuesToMeasure = [];
  
    CombinedStream.call(this);
  
    options = options || {};
    for (var option in options) {
      this[option] = options[option];
    }
  }
docs: Create readable "multipart/form-data" streams.
  Can be used to submit forms
  and file uploads to other web applications.
  
  @constructor
  @param {Object} options - Properties to be added/overriden for FormData and CombinedStream