code: def test_register(capsys):
      try:
          assert not Callback.active
          p = ProgressBar()
          p.register()
  
          assert Callback.active
  
          get_threaded(dsk, "e")
          check_bar_completed(capsys)
  
          p.unregister()
  
          assert not Callback.active
      finally:
          Callback.active.clear()
  
file_path: dask/dask/diagnostics/tests/test_progress.py
imports: from __future__ import annotations
  from operator import add, mul
  import pytest
  from dask.callbacks import Callback
  from dask.diagnostics import ProgressBar
  from dask.diagnostics.progress import format_time
  from dask.local import get_sync
  from dask.threaded import get
label_desc: Use image node_id 7 for calling a global function with example usage: test_register(capsys) without return types