code: public function getModuleHandler()
      {
          if (is_null($this->_moduleHandler)) {
              $stem = $this->field;
              if (!isset(self::$_moduleHandlers[$stem])) {
                  self::$_moduleHandlers[$stem] = [];
              }
              $n = count(self::$_moduleHandlers[$stem]);
              $this->_moduleHandler = $this->field . ':_' . $n;
              self::$_moduleHandlers[$stem][] = $this->_moduleHandler;
          }
  
          return $this->_moduleHandler;
      }
docs: Get module handler.
  
  @return [[@doctodo return_type:getModuleHandler]] [[@doctodo return_description:getModuleHandler]]