code: def test_registered(ucx_loop):
      assert "ucx" in backends
      backend = get_backend("ucx")
      assert isinstance(backend, ucx.UCXBackend)
  
file_path: distributed/distributed/comm/tests/test_ucx.py
imports: from __future__ import annotations
  import asyncio
  import os
  from unittest.mock import patch
  import pytest
  import dask
  from distributed.utils import wait_for
  from distributed import Client, Scheduler, wait
  from distributed.comm import connect, listen, parse_address, ucx
  from distributed.comm.core import CommClosedError
  from distributed.comm.registry import backends, get_backend
  from distributed.deploy.local import LocalCluster
  from distributed.diagnostics.nvml import device_get_count, get_device_index_and_uuid, get_device_mig_mode, has_cuda_context
  from distributed.protocol import to_serialize
  from distributed.protocol.utils_test import get_host_array
  from distributed.utils_test import gen_test, inc
label_desc: Use image node_id 1 for calling a global function with example usage: test_registered(ucx_loop) without return types