docs: public static CmsTextMetrics get(Element element, String key) {
  
          CmsTextMetrics instance = null;
          if (key == null) {
              instance = new CmsTextMetrics(key);
              instance.bind(element);
          } else {
              instance = m_instances.get(key);
              if (instance == null) {
                  instance = new CmsTextMetrics(key);
                  instance.bind(element);
                  m_instances.put(key, instance);
              }
          }
          return instance;
      }