src/transformers/models/layoutlmv3/tokenization_layoutlmv3.py/LayoutLMv3Tokenizer/prepare_for_tokenization
class LayoutLMv3Tokenizer:    def prepare_for_tokenization(self, text, is_split_into_words=False, **kwargs):
        add_prefix_space = kwargs.pop("add_prefix_space", self.add_prefix_space)
        # If the text starts with a token that should not be split, no space is added before the text in any case.
        # It's necessary to match the fast tokenization
        if (
            (is_split_into_words or add_prefix_space)
            and (len(text) > 0 and not text[0].isspace())
            and sum([text.startswith(no_split_token) for no_split_token in self.unique_no_split_tokens]) == 0
        ):
            text = " " + text
        return (text, kwargs)