The core of the Python data model architecture is special methods (also known as "magic methods"). These methods, which start ...

The core of the Python data model architecture is the special methods (also known as 'magic methods'). These methods, which ...

Python’s new template strings, or t-strings, give you a much more powerful way to format data than the old-fashioned f-strings.

For that to be possible, either you had to cast from mutable to immutable (which you shouldn't have) or the mutable string derives from the immutable string (which it shouldn't have).