code: def test_init(self):
      assert self.test_backend.model == self.model
      assert self.test_backend.preprocessing == self.preprocessing
      assert self.test_backend.explain_data is None
      assert self.test_backend.state is None
      assert self.test_backend._case
      assert self.test_backend._classes is None
  
imports: import unittest
  from unittest.mock import patch
  import types
  import numpy
  import pandas
  import category_encoders
  from sklearn.ensemble import RandomForestRegressor, RandomForestClassifier
  from pandas.testing import assert_frame_equal, assert_series_equal
  from shapash.backend.base_backend import BaseBackend, _needs_preprocessing
  from shapash.explainer.smart_state import SmartState
label_desc: Use image node_id 3 for calling the TestBaseBackend obj's underlying member method code with example usage: obj.test_init() without return types