Describe the bug
It looks like you get list of encodings from encoding.aliases module.
aliases(as one would/should expect) contains several cases where different keys are mapped to the same value e.g. 1252 and windows_1252 are both mapped to cp1252. You could save time if instead of aliases.keys() you use set(aliases.values()).

BUT THERE'S A WORSE PROBLEM: aliases don't contain codecs that don't have aliases (like cp856, cp874, cp875, cp737, and koi8_u).

To Reproduce
List of encodings, supported by this library:
https://charset-normalizer.readthedocs.io/en/latest/user/support.html#supported-encodings
It's declared that the library supports all encodings which are supported by Python.
But there is no, for example, KOI8-U.

Expected behavior
But KOI8-U is supported (but just it doesn't have an alias):
https://docs.python.org/3.11/library/codecs.html#standard-encodings