code: public function store($data)
      {
          $this->cache[$this->testSessionId] = &$data;
          $encodedData = $this->getStorageFormat()->encode($data);
          
          $this->getStorageService()->set($this->getUserKey(), $this->getStorageKey(), $encodedData);
          \common_Logger::d(sprintf('QtiTimer: Stored %d bytes into state storage', strlen($encodedData)));
  
          return $this;
      }
docs: Stores the timer data
  @param array $data
  @return TimeStorage