def _set(self, obj, value):
        """Internal method to set state, called by meth:`StateTransition.__call__`"""
        if value not in self.lenum:
            raise ValueError("Not a valid value: %s" % value)

        type(obj).__dict__[self.propname].__set__(obj, value)
Internal method to set state, called by meth:`StateTransition.__call__`