code: private void injectExistingEntityTypeAttributeIdentifiers(
        List<? extends EntityType> entityTypes) {
      Map<String, EntityType> existingEntityTypeMap =
          dataService
              .findAll(ENTITY_TYPE_META_DATA, EntityType.class)
              .collect(toMap(EntityType::getId, entityType -> entityType));
  
      entityTypes.forEach(
          entityType -> {
            EntityType existingEntityType = existingEntityTypeMap.get(entityType.getId());
  
            if (existingEntityType != null) {
              entityType.setId(existingEntityType.getId());
  
              Map<String, Attribute> existingAttrs =
                  stream(existingEntityType.getOwnAllAttributes())
                      .collect(toMap(Attribute::getName, Function.identity()));
              entityType
                  .getOwnAllAttributes()
                  .forEach(
                      attr -> {
                        Attribute existingAttr = existingAttrs.get(attr.getName());
                        if (existingAttr != null) {
                          // inject existing attribute identifier
                          attr.setIdentifier(existingAttr.getIdentifier());
                        }
                      });
            }
          });
    }
docs: Inject existing attribute identifiers in system entity types
  
  @param entityTypes system entity types