'If the ModuleSystem is set, set the attr on it.
Always set the attr on the DescriptorSystem.'

def __setattr__(self, name, value):

    if (name in self.__slots__):
        return super(CombinedSystem, self).__setattr__(name, value)
    if self._module_system:
        setattr(self._module_system, name, value)
    setattr(self._descriptor_system, name, value)
