Forgot an abstractmethod

exo/inference/inference_engine.py

@@ -12,6 +12,7 @@ class InferenceEngine(ABC):
   async def encode(self, shard: Shard, prompt: str) -> np.ndarray:
     pass
   
+  @abstractmethod
   async def sample(self, x: np.ndarray) -> np.ndarray:
     pass