code: def prometheus_not_available():
      import sys
  
      with mock.patch.dict("sys.modules", {"prometheus_client": None}):
          sys.modules.pop("distributed.http.worker.prometheus", None)
          yield
  
imports: from __future__ import annotations
  from unittest import mock
  import pytest
  from distributed import Event, Worker, wait
  from distributed.sizeof import sizeof
  from distributed.utils_test import async_poll_for, fetch_metrics, fetch_metrics_body, fetch_metrics_sample_names, gen_cluster
label_desc: Use image node_id 1 for calling a global function with example usage: prometheus_not_available() without return types