v1: adjust range for seed to be compatible with envpool

Author: MischaPanch

tianshou/highlevel/env.py

@@ -389,7 +389,7 @@ def _next_seed(rng: np.random.Generator) -> int:
         :param rng: the random number generator
         :return: the sampled random seed
         """
-        return int(rng.integers(0, 2**64, dtype=np.uint64))
+        return int(rng.integers(-2**31, 2**31, dtype=np.int32)) # int32 is needed for envpool compatibility
 
     @abstractmethod
     def _create_env(self, mode: EnvMode) -> Env: