code: public boolean isPersistent(DbEntity dbEntity) {
      CachedDbEntity cachedDbEntity = getCachedEntity(dbEntity);
      if(cachedDbEntity == null) {
        return false;
      } else {
        return cachedDbEntity.getEntityState() == PERSISTENT;
      }
    }
docs: Allows checking whether the provided entity is present in the cache
  and is {@link DbEntityState#PERSISTENT}.
  
  @param dbEntity the entity to check
  @return true if the provided entity is present in the cache and is
  {@link DbEntityState#PERSISTENT}.