code: public static <T> void call(RpcCallable<T> callable, StreamObserver<T> responseObserver) {
      try {
        T ret = callable.call();
        responseObserver.onNext(ret);
        responseObserver.onCompleted();
      } catch (AlluxioException e) {
        responseObserver
            .onError(AlluxioStatusException.fromAlluxioException(e).toGrpcStatusException());
      } catch (RuntimeException e) {
        responseObserver.onError(new InternalException(e).toGrpcStatusException());
      }
    }
docs: Calls the given {@link RpcCallable} and handles any exceptions thrown. No call history or
  errors will be logged. This method should be used for internal RPCs.
  
  @param callable the callable to call
  @param <T> the return type of the callable
  @param responseObserver gRPC response observer