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