Cannot tokenize byte sequences that are not valid UTF-8 due to design flaw

Hello,

The BPE algorithm is capable of tokenizing any byte sequence, and LLMs generally accept any sequence of tokens and use token dictionaries that can successfully represent any byte sequence, but the encode method in bpe-openai accepts a type that has to be valid UTF-8. So there are lots of byte sequences, many of which are only 1 byte long, which you cannot tokenize using this library.

まず、bpe-openai の encode メソッドと、それが受け付ける入力型を調査します。ライブラリが任意のバイト列をどのように公開すべきかを判断し、無効な UTF-8 入力のテストカバレッジを追加して、すべてのバイト列をトークン化できることを検証します。

索引モデルが issue の本文から書いたものです。