code: def test_gray_code(self):
      input_expected_output = {
          (0, 0): [0],
          (0, 1): [0],
          (0, 3): [0, 0, 0],
          (1, 1): [1],
          (1, 3): [0, 0, 1],
          (2, 2): [1, 1],
          (13, 4): [1, 0, 1, 1],
          (13, 6): [0, 0, 1, 0, 1, 1],
      }
      for test_input, expected_output in input_expected_output.items():
          n, n_bits = test_input
          out = encoders.GrayEncoder.gray_code(n, n_bits)
          self.assertEqual(out, expected_output)
  
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 3 for calling the TestGrayEncoder obj's underlying member method code with example usage: obj.test_gray_code() without return types