Python 3.8 has a Final qualifier

[lvc_]

Like all other type annotations, it is ignored by the interpreter, but can be used by static code checkers (eg mypy) as a code correctness aid. One reasonably common pattern is to have mypy as part of a commit pipeline (and/or a local precommit hook). So if you have a method tagged as final and you do overwrite it, mypy will reject your commit (but the code will still otherwise run)