src/transformers/models/whisper/english_normalizer.py/BasicTextNormalizer/__call__
class BasicTextNormalizer:    def __call__(self, s: str):
        s = s.lower()
        s = re.sub(r"[<\[][^>\]]*[>\]]", "", s)  # remove words between brackets
        s = re.sub(r"\(([^)]+?)\)", "", s)  # remove words between parenthesis
        s = self.clean(s).lower()

        if self.split_letters:
            s = " ".join(regex.findall(r"\X", s, regex.U))

        s = re.sub(r"\s+", " ", s)  # replace any successive whitespace characters with a space

        return s