code: def test_deprecated_endpoint(self):
      response = self.fetch("/st-metrics")
  
      self.assertEqual(200, response.code)
      self.assertEqual(
          response.headers["link"],
          f'<http://127.0.0.1:{self.get_http_port()}/_stcore/metrics>; rel="alternate"',
      )
      self.assertEqual(response.headers["deprecation"], "True")
  
file_path: streamlit/lib/tests/streamlit/web/server/stats_handler_test.py
imports: from unittest.mock import MagicMock
  import tornado.testing
  import tornado.web
  from google.protobuf.json_format import MessageToDict
  from tornado.httputil import HTTPHeaders
  from streamlit.proto.openmetrics_data_model_pb2 import MetricSet
  from streamlit.runtime.stats import CacheStat
  from streamlit.web.server.server import METRIC_ENDPOINT
  from streamlit.web.server.stats_request_handler import StatsRequestHandler
label_desc: Use image node_id 3 for calling the StatsHandlerTest obj's underlying member method code with example usage: obj.test_deprecated_endpoint() without return types