class_docstr: Class for representation test cases. Most tests are
  parameterized, some are implemented individually
  (e.g. to test a formula manually).
code: def test_normalize_DataFrame_also_as_output(self):
      # normalize should also return DataFrame output for DataFrame
      # input so we test it separately
      result = representation.normalize(df)
      correct_output = pd.DataFrame(
          [[1.0, 0.0], [0.0, 0.0]],
          index=[5, 7],
          columns=["a", "b"],
      )
  
      pd.testing.assert_frame_equal(
          result,
          correct_output,
          check_dtype=False,
          rtol=0.1,
          atol=0.1,
      )
  
imports: import pandas
  import numpy
  from texthero import representation
  from texthero import preprocessing
  import pytest
  from .conftest import broken_case
  import doctest
  import unittest
  import string
  import math
  import warnings
  from parameterized import parameterized
label_desc: Use image node_id 8 for calling the TestAbstractRepresentation obj's underlying member method code with example usage: obj.test_normalize_DataFrame_also_as_output() without return types