code: def fit(self, X, y=None, **kwargs):
      return self
  
imports: import os
  import pytest
  from unittest import mock
  from yellowbrick.base import Visualizer
  from yellowbrick.pipeline import VisualPipeline
  from sklearn.pipeline import Pipeline
  from sklearn.base import BaseEstimator, TransformerMixin
label_desc: Use image node_id 1 for calling the MockTransformer obj's underlying member method code with example usage: obj.fit(X, y) and returns: self