Now you have two sets of characters: one with the vocabulary from the dataset and one with the vocabulary from the tokenizer. 
To identify any unsupported characters in the dataset, you can take the difference between these two sets. The resulting 
set will contain the characters that are in the dataset but not in the tokenizer.

dataset_vocab - tokenizer_vocab
{' ', 'à', 'ç', 'è', 'ë', 'í', 'ï', 'ö', 'ü'}