def add_empty_to_cache(self, idx, trajectory_idx, replica_idx, bias):
obj = Sample(
trajectory=self.storage.trajectories[int(trajectory_idx)],
replica=int(replica_idx),
bias=float(bias)
)
obj.idx[self.storage] = idx
obj._origin = self.storage
del obj.details
del obj.ensemble
del obj.mover
del obj.parent
self.cache[idx] = obj
return obj
