input: 
  def classify_emails_naive_bayes(X_train, y_train, X_test):
      """This function constructs a naive Bayes classifier to classify emails as spam or not spam.
      The classifier is trained using GaussianNB from sklearn.
      >>> classify_emails_naive_bayes(X_train, y_train, X_test)
      array([1, 0, 1, 0, 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)
      # Predict Output 
      y_pred = model.predict(X_test)
      return y_pred
  
output:     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)
      # Predict Output 
      y_pred = model.predict(X_test)
      return y_pred