input: def evaluate_model_accuracy(clf, X_train, y_train, X_test, y_test):
      """ Evaluate the accuracy of a given machine-learning model.
      >>> from sklearn.svm import SVC
      >>> clf = SVC(kernel='poly', degree=2, gamma=0.05)
      >>> evaluate_model_accuracy(clf, X_train, y_train, X_test, y_test)
      Accuracy: 0.85
      """
      clf.fit(X_train, y_train)
      y_pred = clf.predict(X_test)
      accuracy = accuracy_score(y_test, y_pred)
      return "Accuracy: " + str(accuracy)
output:     from sklearn.metrics import accuracy_score