presto-main/src/main/java/io/prestosql/operator/exchange/BroadcastExchanger.java/BroadcastExchanger/BroadcastExchanger
class BroadcastExchanger:    public BroadcastExchanger(List<Consumer<PageReference>> buffers, LocalExchangeMemoryManager memoryManager)
    {
        this.buffers = ImmutableList.copyOf(requireNonNull(buffers, "buffers is null"));
        this.memoryManager = requireNonNull(memoryManager, "memoryManager is null");
    }