code: def add(self, text):
          
          if self._is_stringable(text) or self._is_qstring(text):
              self.text.append(PlainText(text))
          elif isinstance(text, Text):
              self.text.append(text)
          elif text is None or (hasattr(text, 'isNull') and text.isNull()):
              self.text.append(PlainText(
                  tr('None or Null found from the data.')))
          else:
              raise InvalidMessageItemError(text, text.__class__)
docs: add a Text MessageElement to the existing Text
  
          Strings can be passed and are automatically converted in to
          item.Text()
  
          :param text: An element to add to the text.
          :type text: str