def to_sax(self, instance, dest):
        """
        Take the object associated with this descriptor on `instance` and
        serialize it as child into the given :class:`lxml.etree.Element`
        `parent`.

        If the object is :data:`None`, no content is generated.
        """
        obj = self.__get__(instance, type(instance))
        if obj is None:
            return
        obj.unparse_to_sax(dest)
Take the object associated with this descriptor on `instance` and
        serialize it as child into the given :class:`lxml.etree.Element`
        `parent`.

        If the object is :data:`None`, no content is generated.