@RequiresSession
  public StageEntity findByPK(StageEntityPK stageEntityPK) {
    return entityManagerProvider.get().find(StageEntity.class, stageEntityPK);
  }
Mapping of valid status transitions that that are driven by manual input.
ambari-server/src/main/java/org/apache/ambari/server/orm/dao/StageDAO.java