training_utils/config.py: inline type alias

Follow up of #227

src/refiners/training_utils/config.py

@@ -1,23 +1,24 @@
 from enum import Enum
 from logging import warn
 from pathlib import Path
-from typing import Any, Callable, Literal, Type, TypeVar
+from typing import Any, Callable, Iterable, Literal, Type, TypeVar
 
 import tomli
 from bitsandbytes.optim import AdamW8bit, Lion8bit  # type: ignore
 from prodigyopt import Prodigy  # type: ignore
 from pydantic import BaseModel, validator
+from torch import Tensor
 from torch.optim import SGD, Adam, AdamW, Optimizer
-
-try:
-    from torch.optim.optimizer import params_t as ParamsT  # PyTorch 2.1. TODO: remove "soon"
-except ImportError as e:
-    from torch.optim.optimizer import ParamsT
 from typing_extensions import TypedDict  # https://errors.pydantic.dev/2.0b3/u/typed-dict-version
 
 import refiners.fluxion.layers as fl
 from refiners.training_utils.dropout import apply_dropout, apply_gyro_dropout
 
+# PyTorch optimizer parameters type
+# TODO: replace with `from torch.optim.optimizer import ParamsT` when PyTorch 2.2+ is enforced
+# See https://github.com/pytorch/pytorch/pull/111114
+ParamsT = Iterable[Tensor] | Iterable[dict[str, Any]]
+
 __all__ = [
     "parse_number_unit_field",
     "TimeUnit",