code: def _make_reserved_tokens_re(reserved_tokens):
    
    if not reserved_tokens:
      return None
    escaped_tokens = [_re_escape(rt) for rt in reserved_tokens]
    pattern = "(%s)" % "|".join(escaped_tokens)
    reserved_tokens_re = _re_compile(pattern)
    return reserved_tokens_re
docs: Constructs compiled regex to parse out reserved tokens.