docstr: test handle_categorical_missing
docstr_tok: ["test","handle_categorical_missing"]
code: def handle_categorical_missing(self):
      """
      test handle_categorical_missing
      """
      df_test = pd.DataFrame(
          {
              "city": [np.nan, "paris", "chicago"],
              "state": ["US", "FR", "FR"],
              "other": [np.nan, "B", "B"],
          }
      )
  
      df_test = handle_categorical_missing(df_test)
  
      df_expected = pd.DataFrame(
          {
              "city": ["missing", "paris", "chicago"],
              "state": ["US", "FR", "FR"],
              "other": ["missing", "B", "B"],
          }
      )
  
      assert_frame_equal(df_test, df_expected)
  
file_path: shapash/tests/unit_tests/utils/test_transform.py
imports: import unittest
  import pandas
  import numpy
  from sklearn.compose import ColumnTransformer
  import sklearn.preprocessing
  import category_encoders
  from shapash.utils.transform import get_preprocessing_mapping, get_features_transform_mapping, handle_categorical_missing
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 7 for calling the TestInverseTransformCaterogyEncoder obj's underlying member method code with example usage: obj.handle_categorical_missing() without return types