This model has not been trained on any Cantonese material.
It is simply a base model in which the embeddings and tokenizer were patched with Cantonese characters. One can find the original model gpt2-tiny-chinese.
I used this repo to identify missing Cantonese characters
After identifying the missing characters, the Huggingface library provides very high level API to modify the tokenizer and embeddings.
Download a tokenizer and a model from the Huggingface library. Then:
tokenizer.add_tokens("your new tokens")
model.resize_token_embeddings(len(tokenizer))
tokenizer.push_to_hub("your model name")