code: def prometheus_backend_port():
      port = random_port()
      os.environ["PROMETHEUS_BACKEND_PORT"] = str(port)
      yield port
      del os.environ["PROMETHEUS_BACKEND_PORT"]
  
file_path: jina/tests/integration/instrumentation/conftest.py
imports: import os
  import time
  import pytest
  from prometheus_api_client import PrometheusConnect
  from jina.helper import random_port
label_desc: Use image node_id 2 for calling a global function with example usage: prometheus_backend_port() without return types