I believe there's an error in the Matrix class that is published on the website.
We are not asked to create a "multiply_by_scalar" method so I assumed it is fully operational, yet when you actually try to multiply any Matrix object by a number, Python gets angry and pops up an error:
"AttributeError: 'Matrix' object has no attribute 'operator' "
Double checked and in fact "operator" is not mentioned anywhere in the code other than when it is called. Needs a fix or am I missing something?