input: def classify_emails(X_train, y_train, X_test):
      """ Construct a naive bayes classifier using python to classify emails as spam or not spam.
      >>> classify_emails([[1, 2], [2, 3]], [0, 1], [[1, 1]])
      [0]
      >>> classify_emails([[0, 0], [1, 1]], [1, 0], [[0, 1]])
      [1]
      """
      from sklearn.naive_bayes import GaussianNB
      model = GaussianNB()
      model.fit(X_train, y_train)
      y_pred = model.predict(X_test)
      return y_pred
output:     from sklearn.naive_bayes import GaussianNB
      model = GaussianNB()
      model.fit(X_train, y_train)
      y_pred = model.predict(X_test)
      return y_pred