code: def test_callback_active():
      """Test that callbacks are active within context"""
      assert not RayDaskCallback.ray_active
  
      with RayDaskCallback():
          assert RayDaskCallback.ray_active
  
      assert not RayDaskCallback.ray_active
  
file_path: ray/python/ray/util/dask/tests/test_dask_callback.py
imports: import dask
  import pytest
  import ray
  from ray.util.dask import ray_dask_get, RayDaskCallback
label_desc: Use image node_id 3 for calling a global function with example usage: test_callback_active() without return types