presto-main/src/main/java/io/prestosql/server/TaskUpdateRequest.java/TaskUpdateRequest/toString
class TaskUpdateRequest:    @Override
    public String toString()
    {
        return toStringHelper(this)
                .add("session", session)
                .add("extraCredentials", extraCredentials.keySet())
                .add("fragment", fragment)
                .add("sources", sources)
                .add("outputIds", outputIds)
                .add("totalPartitions", totalPartitions)
                .toString();
    }