protected function guardRequiredState()
 {
     parent::guardRequiredState();
     Assertion::isArray($this->data);
     $mandatory_attribute_names = ['identifier', 'uuid', 'language', 'version', 'workflow_state'];
     foreach ($mandatory_attribute_names as $attribute_name) {
         Assertion::keyExists($this->data, $attribute_name, 'mandatory');
     }
 }
 protected function guardRequiredState()
 {
     parent::guardRequiredState();
     Assertion::isArray($this->data);
 }