NotFittedError: 'This scikit-learn model is not fitted yet' when partial_fit not supported
The NotFittedError with message 'This scikit-learn model is not fitted yet' is raised when calling predict or score on an estimator that has not been fitted, as documented in the scikit-learn reference. Not all estimators implement the partial_fit method, creating an unclear API for incremental learning; LinearRegression lacks it while SGDClassifier supports