private function getPluginConfig($pluginId) {
    if (!array_key_exists(static::CONFIG_KEY, $this->installState)) {
      return [];
    }

    if (!array_key_exists($pluginId, $this->installState[static::CONFIG_KEY])) {
      return [];
    }

    return $this->installState[static::CONFIG_KEY][$pluginId];
  }