code: def test_inverse_transform_when_encode_unseen():
      df1 = pd.DataFrame(
          {"words": ["dog", "dog", "cat", "cat", "cat", "bird"]}
      )
      df2 = pd.DataFrame(
          {"words": ["dog", "dog", "cat", "cat", "cat", "frog"]}
      )
      y = [1, 0, 1, 0, 1, 0]
      enc = MeanEncoder(unseen="encode")
      enc.fit(df1, y)
      dft = enc.transform(df2)
      with pytest.raises(NotImplementedError):
          enc.inverse_transform(dft)
  
file_path: feature_engine/tests/test_encoding/test_mean_encoder.py
imports: import numpy
  import pandas
  import pytest
  from feature_engine.encoding import MeanEncoder
label_desc: Use image node_id 15 for calling a global function with example usage: test_inverse_transform_when_encode_unseen() without return types