code: def test_check_warns_on_nonexistent():
      with pytest.warns(UserWarning) as cm:
          has_feature = features.check("typo")
      assert has_feature is False
      assert str(cm[-1].message) == "Unknown feature 'typo'."
  
file_path: pillow/Tests/test_features.py
imports: from __future__ import annotations
  import io
  import re
  import pytest
  from PIL import features
  from .helper import skip_unless_feature
label_desc: Use image node_id 10 for calling a global function with example usage: test_check_warns_on_nonexistent() without return types