in bitsandbytes/optim/optimizer.py [0:0]
def to_gpu(self):
for gindex, group in enumerate(self.param_groups):
for pindex, p in enumerate(group['params']):
if p in self.state:
values = self.state[p]
for k, v in values.items():
if isinstance(v, torch.Tensor):
self.state[p][k] = v.to(p.device)