🚀 Feature request

This is a feature request to add Wav2Vec2 Pretraining functionality to the transformers library. This is a "Good Second Issue" feature request, which means that interested contributors should have some experience with the transformers library and ideally also with training/fine-tuning Wav2Vec2.

Motivation

The popular [Wav2Vec2](https://huggingface.co/models?filter=w

The Split class accepts SplitDelimiterBehavior which is really useful. The Punctuation however always uses SplitDelimiterBehavior::Isolated (and Whitespace on the other hand behaves like SplitDelimiterBehavior::Removed).

impl PreTokenizer for Punctuation {
    fn pre_tokenize(&self, pretokenized: &mut PreTokenizedString) -> Result<()> {
        pretokenized.split(|_, s| s.spl

Description

While using tokenizers.create with the model and vocab file for a custom corpus, the code throws an error and is not able to generate the BERT vocab file

Error Message

ValueError: Mismatch vocabulary! All special tokens specified must be control tokens in the sentencepiece vocabulary.

To Reproduce

from gluonnlp.data import tokenizers
tokenizers.create('spm', model_p