code: def worker(self):
          
          if self._worker is None:
              self._worker = XOrbLookupWorker(self.isThreadEnabled())
              
              # create worker connections
              self.loadRequested.connect(self._worker.loadRecords)
              self.loadBatchRequested.connect(self._worker.loadBatch)
              self.loadColumnsRequested.connect(self._worker.loadColumns)
              
              self._worker.loadingStarted.connect(self.markLoadingStarted)
              self._worker.loadingFinished.connect(self.markLoadingFinished)
              self._worker.loadedRecords[object].connect(self._loadRecords)
              self._worker.loadedRecords[object, object].connect(self._loadRecords)
              self._worker.loadedGroup.connect(self.createGroupItem)
              self._worker.columnLoaded.connect(self._loadColumns)
              self._worker.connectionLost.connect(self._connectionLost)
              
          return self._worker
docs: Returns the worker associated with this tree widget.
          
          :return     <projexui.xorblookupworker.XOrbLookupWorker>