'__call__ allows the InstanceState to act as a deferred
callable for loading expired attributes, which is also
serializable (picklable).'

def __call__(self, state, passive):

    if (not (passive & SQL_OK)):
        return PASSIVE_NO_RESULT
    toload = self.expired_attributes.intersection(self.unmodified)
    self.manager.deferred_scalar_loader(self, toload)
    for k in toload.intersection(self.callables):
        del self.callables[k]
    return ATTR_WAS_SET
