code: def add_text(self, text):
          
          t = self._r.add_t(text)
          return _Text(t)
docs: Returns a newly appended |_Text| object (corresponding to a new
          ``<w:t>`` child element) to the run, containing *text*. Compare with
          the possibly more friendly approach of assigning text to the
          :attr:`Run.text` property.