private function validateResolvers(array $resolvers)
    {
        foreach ($resolvers as $index => $resolver) {
            if (!$this->isValidResolver($resolver)) {
                throw new \InvalidArgumentException(sprintf(
                    'Resolver at index %s of type "%s" is not valid resolver type',
                    $index,
                    get_class($resolver)
                ));
            }
        }
    }