code: public List<BeanId> getReferences() {
          if (references == null) {
              return new ArrayList<>();
          }
          ArrayList<BeanId> result = new ArrayList<>();
          for (List<BeanId> b : references.values()) {
              if (b != null) {
                  result.addAll(b);
              }
  
          }
          return result;
      }
docs: Get all references for all properties of this bean.
  
  @return References that identify other beans.