docs: def replace_pattern(tokens, new_pattern):
      """ Given a RegexLexer token dictionary 'tokens', replace all patterns that
          match the token specified in 'new_pattern' with 'new_pattern'.
      """
      for state in tokens.values():
          for index, pattern in enumerate(state):
              if isinstance(pattern, tuple) and pattern[1] == new_pattern[1]:
                  state[index] = new_pattern