docs: function (unused, req) {
              var res = req.res, cb = req.callback;
              if (!cb) {
                  this.$logError(this.MISSING_IO_CALLBACK, [res.url]);
              } else if (res.error != null) {
                  // an error occured
                  // call the error callback
                  if (cb.onerror == null) {
                      // Generic IO error mgt
                      this.$logError(this.IO_REQUEST_FAILED, [res.url, res.error]);
                  } else {
                      var scope = cb.onerrorScope;
                      if (!scope) {
                          scope = cb.scope;
                      }
                      try {
                          cb.onerror.call(scope, res, cb.args);
                      } catch (ex) {
                          this.$logError(this.IO_CALLBACK_ERROR, [res.url], ex);
                      }
                  }
              } else {
  
                  // check the response type to adapt it to the request
                  if (req.expectedResponseType) {
  
                      this._jsonTextConverter(res, req.expectedResponseType);
                  }
  
                  cb.fn.call(cb.scope, res, cb.args);
              }
              req = cb = null;
          }