fix FSDP ShardedGradScaler (#18358)

renaming it

src/transformers/trainer.py

@@ -565,9 +565,11 @@ class Trainer:
                     self.scaler = ShardedGradScaler()
                 elif self.fsdp is not None:
                     if self.amp_dtype == torch.float16:
-                        from torch.distributed.fsdp.sharded_grad_scaler import ShardedGradScaler
+                        from torch.distributed.fsdp.sharded_grad_scaler import (
+                            ShardedGradScaler as FSDPShardedGradScaler,
+                        )
 
-                        self.scaler = ShardedGradScaler()
+                        self.scaler = FSDPShardedGradScaler()
                     else:
                         self.do_grad_scaling = False
                         self.use_cuda_amp = False
@@ -1366,6 +1368,8 @@ class Trainer:
                     transformer_cls_to_wrap = get_module_class_from_name(
                         model, self.args.fsdp_transformer_layer_cls_to_wrap
                     )
+                    if transformer_cls_to_wrap is None:
+                        raise Exception("Could not find the transformer layer class to wrap in the model.")
                     auto_wrap_policy = functools.partial(
                         transformer_auto_wrap_policy,
                         # Transformer layer class to wrap