class RepositoryFactory
{
    public function getRepository(string clazz)
    {
        ...
    }
}

class RepositoryFactory
{
    private function checkClassExistence(string clazz)
    {
        ...
    }
}

class RepositoryFactory
{
    protected function isValidRepositoryClazz(string clazz)
    {
        ...
    }
}