Add a read/write ``{prop_name}`` property to the element class that
        returns the interpreted value of this attribute on access and changes
        the attribute value to its ST_* counterpart on assignment.

def _add_attr_property(self):
        """
        Add a read/write ``{prop_name}`` property to the element class that
        returns the interpreted value of this attribute on access and changes
        the attribute value to its ST_* counterpart on assignment.
        """
        property_ = property(self._getter, self._setter, None)
        # assign unconditionally to overwrite element name definition
        setattr(self._element_cls, self._prop_name, property_)