code: def __init__(self):
      self.variables = None
  
file_path: feature_engine/tests/test_base_transformers/test_base_numerical_transformer.py
imports: import pytest
  from numpy import inf
  from pandas.testing import assert_frame_equal
  from feature_engine._base_transformers.base_numerical import BaseNumericalTransformer
  from tests.estimator_checks.non_fitted_error_checks import check_raises_non_fitted_error
label_desc: Use image node_id 1 to create a new MockClass object from inherited base classes: BaseNumericalTransformer with example: obj = MockClass()