ensure seed is set for VLLM sampling params

PiperOrigin-RevId: 875753179

Author: s-noghabi

tunix/generate/vllm_sampler.py

@@ -415,6 +415,9 @@ def __call__(
       if top_k is not None:
         sampling_params.top_k = top_k
 
+      if seed is not None:
+        sampling_params.seed = seed
+
       if kwargs:
         try:
           sampling_params.update(**kwargs)