code: private boolean canCleanStagingData(JobState jobState)
        throws IOException {
      return this.jobContext.getSemantics() != DeliverySemantics.EXACTLY_ONCE || !this.jobContext.getCommitSequenceStore()
          .get().exists(jobState.getJobName());
    }
docs: Staging data cannot be cleaned if exactly once semantics is used, and the job has unfinished
  commit sequences.