private function getFieldArgTypeNode($type, $fieldName, $argName)
    {
        $fieldArgNode = $this->getFieldArgNode($type, $fieldName, $argName);

        return $fieldArgNode ? $fieldArgNode->type : null;
    }
private function getFieldArgTypeNode($type, $fieldName, $argName)
    {
        $fieldArgNode = $this->getFieldArgNode($type, $fieldName, $argName);

        return $fieldArgNode ? $fieldArgNode->type : null;
    }
@param ObjectType|InterfaceType $type
@param string                   $fieldName
@param string                   $argName

@return TypeNode|null