presto-spi/src/main/java/io/prestosql/spi/block/AbstractSingleMapBlock.java/AbstractSingleMapBlock/isNull
class AbstractSingleMapBlock:    @Override
    public boolean isNull(int position)
    {
        position = getAbsolutePosition(position);
        if (position % 2 == 0) {
            if (getRawKeyBlock().isNull(position / 2)) {
                throw new IllegalStateException("Map key is null");
            }
            return false;
        }
        else {
            return getRawValueBlock().isNull(position / 2);
        }
    }