/**
  * Get the set of required options.
  *
  * @since 0.1.0
  *
  * @return array|null
  */
 public function getRequiredOptions()
 {
     if (!$this->required) {
         return null;
     }
     if ($this->required instanceof ConfigInterface) {
         return $this->required->getArrayCopy();
     }
     return (array) $this->required;
 }