Update Optional[x] -> x | None and Union[x, y] to x | y (#26633)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>

vllm/reasoning/step3_reasoning_parser.py

@@ -2,7 +2,6 @@
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 
 from collections.abc import Sequence
-from typing import Optional, Union
 
 import regex as re
 from transformers import PreTrainedTokenizerBase
@@ -50,7 +49,7 @@ class Step3ReasoningParser(ReasoningParser):
         previous_token_ids: Sequence[int],
         current_token_ids: Sequence[int],
         delta_token_ids: Sequence[int],
-    ) -> Union[DeltaMessage, None]:
+    ) -> DeltaMessage | None:
         """
         Extract reasoning content from a delta message.
         Handles streaming output where previous + delta = current.
@@ -81,7 +80,7 @@ class Step3ReasoningParser(ReasoningParser):
 
     def extract_reasoning_content(
         self, model_output: str, request: ChatCompletionRequest
-    ) -> tuple[Optional[str], Optional[str]]:
+    ) -> tuple[str | None, str | None]:
         # Check if the model output contains the </think> token
         if self.think_end_token not in model_output:
             # If no </think> token, everything is reasoning content