docs: @Override
      public ConfigurablePortletEnvironment getEnvironment() {
          ConfigurableEnvironment env = super.getEnvironment();
          Assert.isInstanceOf(ConfigurablePortletEnvironment.class, env,
                  "ConfigurablePortletApplicationContext environment must be of type " +
                  "ConfigurablePortletEnvironment");
          return (ConfigurablePortletEnvironment) env;
      }