code: public DbBulkOperation deletePreserveOrder(Class<? extends DbEntity> entityType, String statement, Object parameter) {
      return performBulkOperationPreserveOrder(entityType, statement, parameter, DELETE_BULK);
    }
docs: Several delete operations added by this method will be executed preserving the order of method calls, no matter what entity type they refer to.
  They will though be executed after all "not-bulk" operations (e.g. {@link DbEntityManager#insert(DbEntity)} or {@link DbEntityManager#merge(DbEntity)})
  and after those deletes added by {@link DbEntityManager#delete(Class, String, Object)}.
  @param entityType
  @param statement
  @param parameter
  @return delete operation