code: public void initializeSubContainers(CmsContainerPageElementPanel containerElement) {
  
          int containerCount = m_targetContainers.size();
          m_targetContainers.putAll(m_containerpageUtil.consumeContainers(m_containers, containerElement.getElement()));
          updateContainerLevelInfo();
          if (m_targetContainers.size() > containerCount) {
              // in case new containers have been added, the gallery data needs to be updated
              scheduleGalleryUpdate();
          }
      }
docs: Checks for element sub containers.<p>
  
  @param containerElement the container element