docs: private void checkCollectionForeignkeys(ModelDef modelDef, String checkLevel) throws ConstraintException
      {
          if (CHECKLEVEL_NONE.equals(checkLevel))
          {
              return;
          }
  
          ClassDescriptorDef      classDef;
          CollectionDescriptorDef collDef;
  
          for (Iterator it = modelDef.getClasses(); it.hasNext();)
          {
              classDef = (ClassDescriptorDef)it.next();
              for (Iterator collIt = classDef.getCollections(); collIt.hasNext();)
              {
                  collDef = (CollectionDescriptorDef)collIt.next();
                  if (!collDef.getBooleanProperty(PropertyHelper.OJB_PROPERTY_IGNORE, false))
                  {
                      if (collDef.hasProperty(PropertyHelper.OJB_PROPERTY_INDIRECTION_TABLE))
                      {
                          checkIndirectionTable(modelDef, collDef);
                      }
                      else
                      {    
                          checkCollectionForeignkeys(modelDef, collDef);
                      }
                  }
              }
          }
      }