code: def fit(self, X, y=None, **kwargs):
      # We need to ensure that sklearn can tell the estimator is fitted
      self.fitted_ = True
      return self
  
file_path: fairlearn/test/install/test_no_matplotlib.py
imports: import numpy
  import pytest
  from sklearn.base import BaseEstimator, ClassifierMixin
  from fairlearn.postprocessing import ThresholdOptimizer, plot_threshold_optimizer
  from fairlearn.postprocessing._constants import _MATPLOTLIB_IMPORT_ERROR_MESSAGE
  from fairlearn.metrics import plot_model_comparison
  from fairlearn.postprocessing._threshold_optimizer import SIMPLE_CONSTRAINTS
label_desc: Use image node_id 1 for calling the FakePredictor obj's underlying member method code with example usage: obj.fit(X, y) and returns: self