class_docstr: Used to check output of featureunions
class_docstr_tok: ["Used","to","check","output","of","featureunions"]
code: def fit(self, X, y):
      assert (X == self.expected_X).all()
      assert len(X) == len(y)
      return self
  
imports: import os
  from ast import literal_eval
  import numpy
  from distributed import Lock, Variable, get_worker
  from sklearn.base import BaseEstimator, ClassifierMixin
  from sklearn.utils.validation import _num_samples, check_array
label_desc: Use image node_id 2 for calling the CheckXClassifier obj's underlying member method code with example usage: obj.fit(X, y) and returns: self