Bind an instance to this Pangler, using the bound Pangler store.

        This method functions identically to `bind`, except that it might
        return a Pangler which was previously bound to the provided instance.

def stored_bind(self, instance):
        """Bind an instance to this Pangler, using the bound Pangler store.

        This method functions identically to `bind`, except that it might
        return a Pangler which was previously bound to the provided instance.

        """

        if self.id is None:
            return self.bind(instance)

        store = self._bound_pangler_store.setdefault(instance, {})
        p = store.get(self.id)
        if p is None:
            p = store[self.id] = self.bind(instance)
        return p