code: def test_common_norm_warning(self, long_df, triple_args):
      h = Hist(common_norm=["b"])
      with pytest.warns(UserWarning, match=r"Undefined variable\(s\)"):
          h(long_df, *triple_args)
  
imports: import numpy
  import pandas
  import pytest
  from numpy.testing import assert_array_equal
  from seaborn._core.groupby import GroupBy
  from seaborn._stats.counting import Hist, Count
label_desc: Use image node_id 23 for calling the TestHist obj's underlying member method code with example usage: obj.test_common_norm_warning(long_df, triple_args) without return types