public static Optional<Integer> getChunkSize() {
        if (policy.isPooled()) {
            return Optional.of(((PooledByteBufAllocatorMetric) metric).chunkSize());
        }
        return Optional.empty();
    }
Get the chunk size of the allocator.
It returns {@link Optional#empty} if the {@link #policy} is not {@link ByteBufAllocPolicy#isPooled}.
s3stream/src/main/java/com/automq/stream/s3/ByteBufAlloc.java