presto-main/src/main/java/io/prestosql/execution/TaskSource.java/TaskSource/toString
class TaskSource:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("planNodeId", planNodeId)
                .add("splits", splits)
                .add("noMoreSplits", noMoreSplits)
                .toString();
    }