docs: public void addRefs(Multimap<BeanId, JpaRef> queryRefs) {
          refs.putAll(queryRefs);
          for (BeanId id : refs.keySet()) {
              putIfAbsent(id);
              for (JpaRef ref : refs.get(id)) {
                  putIfAbsent(ref.getTarget());
              }
          }
      }