In Bonus Chapter 1, on Page 10, in the first code block (B1-8), in the last line of said code block, you have written, "y_right = ridge_estimator.predict([[x_right]]]])". This has two extra right square brackets. In figure B1-9, later that same page, at the bottom, you have a correct version of the line of code, "y_right = ridge_estimator.predict([[x_right]])". Since I didn't see this yet listed in the errata, I thought I should point it out.