Create a new worker instance.

def _create_worker(self, method, *args, **kwargs):
        """Create a new worker instance."""
        thread = QThread()
        worker = RequestsDownloadWorker(method, args, kwargs)
        worker.moveToThread(thread)
        worker.sig_finished.connect(self._start)
        self._sig_download_finished.connect(worker.sig_download_finished)
        self._sig_download_progress.connect(worker.sig_download_progress)
        worker.sig_finished.connect(thread.quit)
        thread.started.connect(worker.start)
        self._queue.append(thread)
        self._threads.append(thread)
        self._workers.append(worker)
        self._start()
        return worker