private function ensureBootstrap(string $bootstrapClass)
    {
        if (!is_subclass_of($bootstrapClass, AbstractKernelBootstrap::class)) {
            throw new InvalidArgumentException(
                sprintf('Class "%s" must be a subclass of "%s".', $bootstrapClass, AbstractKernelBootstrap::class)
            );
        }
    }
private function ensureBootstrap(string $bootstrapClass)
    {
        if (!is_subclass_of($bootstrapClass, AbstractKernelBootstrap::class)) {
            throw new InvalidArgumentException(
                sprintf('Class "%s" must be a subclass of "%s".', $bootstrapClass, AbstractKernelBootstrap::class)
            );
        }
    }
private function ensureBootstrap ( string $ bootstrapClass ) { if ( ! is_subclass_of ( $ bootstrapClass , AbstractKernelBootstrap :: class ) ) { throw new InvalidArgumentException ( sprintf ( 'Class "%s" must be a subclass of "%s".' , $ bootstrapClass , AbstractKernelBootstrap :: class ) ) ; } }
Ensures bootstrap class extends abstract kernel bootstrap.

@param string $bootstrapClass
@throws InvalidArgumentException
Ensures bootstrap class extends abstract kernel bootstrap .