code: def _wait_for_transfer_threads(self, terminate):
          # type: (SyncCopy, bool) -> None
          
          if terminate:
              self._synccopy_terminate = terminate
          for thr in self._transfer_threads:
              blobxfer.util.join_thread(thr)
docs: Wait for download threads
          :param SyncCopy self: this
          :param bool terminate: terminate threads