code: def extract_plain_text(self, reduce: bool = False) -> str:
          
          if reduce:
              self.reduce()
  
          result = ''
          for seg in self:
              if seg.type == 'text':
                  result += ' ' + seg.data['text']
          if result:
              result = result[1:]
          return result
docs: Extract text segments from the message, joined by single space.
  
          :param reduce: reduce the message before extracting
          :return: the joined string