Cross Validation (sklearn train test split) - ValueError: not enough values to unpack
Sklearn expects to get X and y in train_test_split().

X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.33, random_state=42)


You only parse X.

See the docs: https://scikit-learn.org/stable/modules/generated/sklearn.model_selection.train_test_split.html