code: private function getDeprecationReason($node)
      {
          $deprecated = Values::getDirectiveValues(Directive::deprecatedDirective(), $node);
  
          return $deprecated['reason'] ?? null;
      }
docs: Given a collection of directives, returns the string value for the
  deprecation reason.
  
  @param EnumValueDefinitionNode | FieldDefinitionNode $node
  
  @return string