[legacy] clean up legacy code (#4743)

* [legacy] remove outdated codes of pipeline (#4692)

* [legacy] remove cli of benchmark and update optim (#4690)

* [legacy] remove cli of benchmark and update optim

* [doc] fix cli doc test

* [legacy] fix engine clip grad norm

* [legacy] remove outdated colo tensor (#4694)

* [legacy] remove outdated colo tensor

* [test] fix test import

* [legacy] move outdated zero to legacy (#4696)

* [legacy] clean up utils (#4700)

* [legacy] clean up utils

* [example] update examples

* [legacy] clean up amp

* [legacy] fix amp module

* [legacy] clean up gpc (#4742)

* [legacy] clean up context

* [legacy] clean core, constants and global vars

* [legacy] refactor initialize

* [example] fix examples ci

* [example] fix examples ci

* [legacy] fix tests

* [example] fix gpt example

* [example] fix examples ci

* [devops] fix ci installation

* [example] fix examples ci

colossalai/checkpoint_io/utils.py

@@ -13,7 +13,6 @@ import torch.nn as nn
 from torch.optim import Optimizer
 
 from colossalai.interface import ModelWrapper, OptimizerWrapper
-from colossalai.nn.optimizer import ColossalaiOptimizer
 from colossalai.tensor.d_tensor import (
     is_customized_distributed_tensor,
     is_distributed_tensor,
@@ -130,10 +129,7 @@ def unwrap_optimizer(optimizer: OptimizerWrapper):
     This method should be used before saving/loading it to/from sharded checkpoints.
     '''
 
-    # TODO(Baizhou): ColossalaiOptimizer will be replaced with OptimizerWrapper in the future
     unwrapped_optim = optimizer.optim
-    if isinstance(unwrapped_optim, ColossalaiOptimizer):
-        unwrapped_optim = unwrapped_optim.optim
     return unwrapped_optim