code: private void addAttributePolling(final AttributeImpl attr) throws DevFailed {
          if (MANAGER == null) {
              startCache();
          }
          removeAttributePolling(attr);
          final AttributeCache cache = new AttributeCache(MANAGER, attr, deviceName, deviceLock, aroundInvoke);
          if (attr.getPollingPeriod() == 0) {
              extTrigAttributeCacheMap.put(attr, cache);
          } else {
              attributeCacheMap.put(attr, cache);
          }
          updatePoolConf();
      }
docs: Add attribute as polled
  
  @param attr
  @throws DevFailed