docs: function (event) {
                  // Do nothing if the request has been cancelled.
                  if (cancelled) {
                      return;
                  }
                  // Cleanup the page.
                  cleanup();
                  // Check whether the response callback has run.
                  if (!finished) {
                      // It hasn't, something went wrong with the request. Return an error via
                      // the Observable error path. All JSONP errors have status 0.
                      observer.error(new HttpErrorResponse({
                          url: url,
                          status: 0,
                          statusText: 'JSONP Error',
                          error: new Error(JSONP_ERR_NO_CALLBACK),
                      }));
                      return;
                  }
                  // Success. body either contains the response body or null if none was
                  // returned.
                  observer.next(new HttpResponse({
                      body: body,
                      status: 200,
                      statusText: 'OK', url: url,
                  }));
                  // Complete the stream, the response is over.
                  observer.complete();
              }