code: def test_fit_classifier():
      """Test fit method of Classifier class."""
      df_train = pd.read_csv("data_for_tests/clean_train.csv")
      y_train = pd.read_csv(
          "data_for_tests/clean_target.csv", squeeze=True
      )
      classifier = Classifier()
      classifier.fit(df_train, y_train)
      assert np.all(classifier._Classifier__col == df_train.columns)
      assert classifier._Classifier__fitOK
  
file_path: MLBox/tests/test_classifier.py
imports: import pytest
  import pandas
  import numpy
  from mlbox.model.classification.classifier import Classifier
  from lightgbm import LGBMClassifier
label_desc: Use image node_id 5 for calling a global function with example usage: test_fit_classifier() without return types