code: def parse_string(self):
          
          if self._parse_string is None:
              parse_text = self._element.xpath('parse/text()')
              if len(parse_text) > 0:
                  self._parse_string = parse_text[0]
          return self._parse_string
docs: Accesses the S-Expression parse string stored on the XML document
  
          :getter: Returns the parse string
          :type: str