code: def test_gray_sorting(self):
      data = np.array(["ba", "ba", "aa"])
      out = encoders.GrayEncoder().fit_transform(data)
      expected = pd.DataFrame(
          [[1, 1], [1, 1], [0, 1]], columns=["0_0", "0_1"]
      )
      pd.testing.assert_frame_equal(out, expected)
  
file_path: category_encoders/tests/test_gray.py
imports: import pandas
  from unittest import TestCase
  import numpy
  import category_encoders
label_desc: Use image node_id 1 for calling the TestGrayEncoder obj's underlying member method code with example usage: obj.test_gray_sorting() without return types