fix: join() raises TypeError when joining bytes collections

[koteshyelamati]

Problem

join([b"foo", b"bar"]) raises TypeError instead of returning b"foobar".

>>> join([b"hello", b" ", b"world"])
TypeError: sequence item 0: expected str instance, bytes found

Root cause

The implementation hardcodes ''.join(colls) — a str join — even when the input is a bytes collection. Python's str.join() cannot accept bytes items.

if isinstance(dest, (bytes, str)):
    return ''.join(colls)  # BUG: always uses str join

Fix

Use cls().join(colls) instead. cls is already computed earlier in the function as dest.__class__, so this naturally dispatches to bytes().join() for bytes and str().join() for strings:

if isinstance(dest, (bytes, str)):
    return cls().join(colls)  # FIX: uses the correct type's join