public static ServerStream getServerStream(final ServerCall<?, ?> call) {
        ServerCall<?, ?> lastServerCall = call;
        if (call instanceof ForwardingServerCall.SimpleForwardingServerCall) {
            lastServerCall = SERVER_CALL_GETTER.get((ForwardingServerCall.SimpleForwardingServerCall<?, ?>) call);
        }
        if (lastServerCall instanceof ServerCallImpl) {
            return STREAM_GETTER.get((ServerCallImpl<?, ?>) lastServerCall);
        }
        return null;
    }
Get grpc's server stream.

@author jiachun.fjc
jraft-extension/rpc-grpc-impl/src/main/java/io/grpc/internal/ServerStreamHelper.java