code: public boolean hasCircleReference(Map<AVObject, Boolean> markMap) {
      if (null == markMap) {
        return false;
      }
      markMap.put(this, true);
      boolean rst = false;
      for (ObjectFieldOperation op: operations.values()) {
        rst = rst || op.checkCircleReference(markMap);
      }
      return rst;
    }
docs: judge operations' value include circle reference or not.
  
  notice: internal used, pls not invoke it.
  
  @param markMap
  @return