code: def test_warning_if_no_language_detected(self, caplog):
      with caplog.at_level(logging.WARNING):
          classifier = TextLanguageRouter()
          classifier.run(text=".")
          assert (
              "Langdetect cannot detect the language of text: ."
              in caplog.text
          )
  
file_path: haystack/test/components/routers/test_text_language_router.py
imports: import logging
  import pytest
  from haystack import Document
  from haystack.components.routers import TextLanguageRouter
label_desc: Use image node_id 7 for calling the TestTextLanguageRouter obj's underlying member method code with example usage: obj.test_warning_if_no_language_detected(caplog) without return types