When the standard says "trust the filename" it is talking to the
application, not to the sniffing library. The library should provide the
tool for applications to follow the standard, but I don't see a reason why
we would have to enforce how applications call the library. Since we agree
there are use cases beyond what the standard has thought of for combining
sniffing the data and guessing based on the filename, we should make that
possible, the standard's exhortations notwithstanding.

Python is not a browser; a browser could be an application written in
Python. Python therefulre should provide tools that are useful to implement
a browser.