input: def construct_naive_bayes_classifier(X_train, y_train, X_test):
      """Constructs a Naive Bayes classifier using the GaussianNB model from
      sklearn to classify emails as spam or not spam.
      >>> model = construct_naive_bayes_classifier([[1, 2], [3, 4]], [0, 1], [[1, 1]])
      >>> model.predict([[1, 1]])
      array([0])
      """
      from sklearn.naive_bayes import GaussianNB
      # Create a Gaussian Classifier
      model = GaussianNB()
      # Train the model using the training sets 
      model.fit(X_train, y_train)
      # Return the classifier
      return model
output:     # Predict the response for test dataset
      y_pred = model.predict(X_test)
      return y_pred