chore: add mypy post training (#2675)

# What does this PR do?
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relevant issues if applicable. -->
This PR adds static type coverage to `llama-stack`

Part of https://github.com/meta-llama/llama-stack/issues/2647

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## Test Plan
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Signed-off-by: Mustafa Elbehery <melbeher@redhat.com>

llama_stack/providers/inline/post_training/torchtune/post_training.py

@@ -123,7 +123,8 @@ class TorchtunePostTrainingImpl:
         training_config: TrainingConfig,
         hyperparam_search_config: dict[str, Any],
         logger_config: dict[str, Any],
-    ) -> PostTrainingJob: ...
+    ) -> PostTrainingJob:
+        raise NotImplementedError()
 
     async def get_training_jobs(self) -> ListPostTrainingJobsResponse:
         return ListPostTrainingJobsResponse(