protected function getConfigValue($key, $defaultValue = null)
 {
     if (array_key_exists($key, $this->configCache)) {
         return $this->configCache[$key];
     }
     $this->configCache[$key] = !empty($this->config) ? $this->config->get($key, $defaultValue) : $defaultValue;
     return $this->configCache[$key];
 }