code: public function resolveType($objectValue, $context, ResolveInfo $info)
      {
          if (isset($this->config['resolveType'])) {
              $fn = $this->config['resolveType'];
  
              return $fn($objectValue, $context, $info);
          }
  
          return null;
      }
docs: Resolves concrete ObjectType for given object value
  
  @param object $objectValue
  @param mixed  $context
  
  @return callable|null