Error in call to target 'torch.optim.adamw.AdamW'

Hello, I am facing this error even though in the config file I have defined the optim like this:
optim:
amp:
enabled: true
amp_dtype: bfloat16
optimizer:
_target_: torch.optim.AdamW

**Error**
Traceback (most recent call last):
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 92, in _call_target
return _target_(*args, **kwargs)
TypeError: AdamW.__init__() missing 1 required positional argument: 'params'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/usr/local/lib/python3.10/dist-packages/torch/multiprocessing/spawn.py", line 90, in _wrap
fn(i, *args)
File "/netscratch/naseem/sam2/training/train.py", line 40, in single_proc_run
trainer = instantiate(cfg.trainer, _recursive_=False)
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 226, in instantiate
return instantiate_node(
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 366, in instantiate_node
cfg[key] = instantiate_node(
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 366, in instantiate_node
cfg[key] = instantiate_node(
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 347, in instantiate_node
return _call_target(_target_, partial, args, kwargs, full_key)
File "/usr/local/lib/python3.10/dist-packages/hydra/_internal/instantiate/_instantiate2.py", line 97, in _call_target
raise InstantiationException(msg) from e
hydra.errors.InstantiationException: Error in call to target 'torch.optim.adamw.AdamW':
TypeError("AdamW.__init__() missing 1 required positional argument: 'params'")
full_key: trainer.optim.optimizer