Use Python 3.9 syntax in examples (#37279)

Signed-off-by: cyy <cyyever@outlook.com>

examples/flax/token-classification/run_flax_ner.py

@@ -1,5 +1,4 @@
 #!/usr/bin/env python
-# coding=utf-8
 # Copyright 2021 The HuggingFace Inc. team. All rights reserved.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -27,7 +26,7 @@ from dataclasses import asdict, dataclass, field
 from enum import Enum
 from itertools import chain
 from pathlib import Path
-from typing import Any, Callable, Dict, Optional, Tuple
+from typing import Any, Callable, Optional
 
 import datasets
 import evaluate
@@ -651,8 +650,8 @@ def main():
 
     # define step functions
     def train_step(
-        state: train_state.TrainState, batch: Dict[str, Array], dropout_rng: PRNGKey
-    ) -> Tuple[train_state.TrainState, float]:
+        state: train_state.TrainState, batch: dict[str, Array], dropout_rng: PRNGKey
+    ) -> tuple[train_state.TrainState, float]:
         """Trains model with an optimizer (both in `state`) on `batch`, returning a pair `(new_state, loss)`."""
         dropout_rng, new_dropout_rng = jax.random.split(dropout_rng)
         targets = batch.pop("labels")