Non-static method GraphQL\Util\StringLiteralFormatter::isVariable() cannot be called statically

[Lenny4]

php -v
PHP 8.2.4 (cli) (built: Mar 14 2023 17:54:25) (ZTS Visual C++ 2019 x64)
Copyright (c) The PHP Group
Zend Engine v4.2.4, Copyright (c) Zend Technologies
    with Xdebug v3.2.0, Copyright (c) 2002-2022, by Derick Rethans

I got error: Non-static method GraphQL\Util\StringLiteralFormatter::isVariable() cannot be called statically when I try to:

$client->runQuery($gql);

When I look in file src/Util/StringLiteralFormatter.php we can see in function formatValueForRHS that isVariable is called statically

While the function doesn't have the static attribute

private function isVariable(string $value): bool