'If the ModuleSystem doesn\'t have an attribute, try returning the same attribute from the
DescriptorSystem, instead. This allows XModuleDescriptors that are bound as XModules
to still function as XModuleDescriptors.'

def __getattr__(self, name):

    try:
        return getattr(self._module_system, name)
    except AttributeError:
        return getattr(self._descriptor_system, name)
