docs: def is_paired(text, open='(', close=')'):
      """Check if the text only contains:
      1. blackslash escaped parentheses, or
      2. parentheses paired.
      """
      count = 0
      escape = False
      for c in text:
          if escape:
              escape = False
          elif c == '\\':
              escape = True
          elif c == open:
              count += 1
          elif c == close:
              if count == 0:
                  return False
              count -= 1
      return count == 0