code: def prometheus_not_available():
      import sys
  
      with mock.patch.dict("sys.modules", {"prometheus_client": None}):
          sys.modules.pop("distributed.http.scheduler.prometheus", None)
          yield
  
file_path: distributed/distributed/http/scheduler/tests/test_scheduler_http.py
imports: from __future__ import annotations
  import asyncio
  import json
  import re
  from unittest import mock
  import pytest
  from tornado.escape import url_escape
  from tornado.httpclient import AsyncHTTPClient, HTTPClientError
  import dask.config
  from dask.sizeof import sizeof
  from distributed import Event, Lock, Scheduler
  from distributed.client import wait
  from distributed.core import Status
  from distributed.utils import is_valid_xml
  from distributed.utils_test import async_poll_for, div, fetch_metrics, fetch_metrics_body, gen_cluster, gen_test, inc, lock_inc, slowinc, wait_for_state
label_desc: Use image node_id 1 for calling a global function with example usage: prometheus_not_available() without return types