code: def test_percent(self, df):
      gb = GroupBy(["null"])
      res = Norm(percent=True)(df, gb, "x", {})
      assert res["y"].max() == pytest.approx(100)
  
imports: from itertools import product
  import numpy
  import pandas
  from pandas.testing import assert_series_equal
  from numpy.testing import assert_array_equal, assert_array_almost_equal
  from seaborn._core.moves import Dodge, Jitter, Shift, Stack, Norm
  from seaborn._core.rules import categorical_order
  from seaborn._core.groupby import GroupBy
  import pytest
label_desc: Use image node_id 5 for calling the TestNorm obj's underlying member method code with example usage: obj.test_percent(df) without return types