getEditableConfigNames

protected function config($name) {
.....

if (in_array($name, $this->getEditableConfigNames())) {
      // Get a mutable object from the factory.
      $config = $config_factory->getEditable($name);
    }
    else {
      $config = $config_factory->get($name);
    }

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这个是怎么回事呢？
当在form类下调用config方法时，
当name在getEditableConfigNames所返回的数组里面，
则调用geteditable表示可以修改，