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

        return $nodes[0] ?? null;
    }
private function getFieldArgNode($type, $fieldName, $argName)
    {
        $nodes = $this->getAllFieldArgNodes($type, $fieldName, $argName);

        return $nodes[0] ?? null;
    }
@param ObjectType|InterfaceType $type
@param string                   $fieldName
@param string                   $argName

@return InputValueDefinitionNode|null