code: def test_matcher_empty_patterns_warns(en_vocab):
      matcher = Matcher(en_vocab)
      assert len(matcher) == 0
      doc = Doc(en_vocab, words=["This", "is", "quite", "something"])
      with pytest.warns(UserWarning):
          matcher(doc)
      assert len(doc.ents) == 0
  
imports: import pytest
  from mock import Mock
  from spacy.matcher import Matcher
  from spacy.tokens import Doc, Span, Token
  from ..doc.test_underscore import clean_underscore
label_desc: Use image node_id 3 for calling a global function with example usage: test_matcher_empty_patterns_warns(en_vocab) without return types