docs: function (request) {
              var iFrame = request.iFrame;
              if (iFrame) {
                  var domEltToRemove = request.iFrameContainer || iFrame;
                  domEltToRemove.parentNode.removeChild(domEltToRemove);
                  // avoid leaks:
                  request.iFrameContainer = null;
                  request.iFrame = null;
                  iFrame.onload = null;
                  iFrame.onreadystatechange = null;
              }
              delete this._requests[request.id];
          }