code: def to_sax(self, instance, dest):
          
  
          value = self.__get__(instance, type(instance))
          if value == self.default:
              return
  
          if self.declare_prefix is not False and self.tag[0]:
              dest.startPrefixMapping(self.declare_prefix, self.tag[0])
          dest.startElementNS(self.tag, None, {})
          try:
              dest.characters(self.type_.format(value))
          finally:
              dest.endElementNS(self.tag, None)
              if self.declare_prefix is not False and self.tag[0]:
                  dest.endPrefixMapping(self.declare_prefix)
docs: Create a child node at `parent` with the tag :attr:`tag`. Set the text
          contents to the value of the attribute which this descriptor represents
          at `instance`.
  
          If the value is :data:`None`, no element is generated.