presto-main/src/main/java/io/prestosql/operator/InterpretedHashGenerator.java/InterpretedHashGenerator/toString
class InterpretedHashGenerator:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("hashChannelTypes", hashChannelTypes)
                .add("hashChannels", hashChannels)
                .toString();
    }