[Typing] Mypy typing part 2 (#4043)

Co-authored-by: SangBin Cho <sangcho@sangcho-LT93GQWG9C.local>

vllm/model_executor/guided_decoding/outlines_decoding.py

@@ -55,7 +55,7 @@ global_thread_pool = None  # used for generating logits processor fsm
 
 async def get_outlines_guided_decoding_logits_processor(
         request: Union[CompletionRequest, ChatCompletionRequest],
-        tokenizer) -> Union[JSONLogitsProcessor, RegexLogitsProcessor]:
+        tokenizer) -> Union[JSONLogitsProcessor, RegexLogitsProcessor, None]:
     """
     Given an OpenAI-compatible request, check for guided decoding parameters
     and get the necessary logits processor for the given guide.
@@ -84,7 +84,7 @@ async def get_outlines_guided_decoding_logits_processor(
 
 def _get_guide_and_mode(
     request: Union[CompletionRequest, ChatCompletionRequest]
-) -> Tuple[str, GuidedDecodingMode]:
+) -> Union[Tuple[str, GuidedDecodingMode], Tuple[None, None]]:
 
     if request.guided_json:
         json = request.guided_json