public function indexExists($index)
    {
        if (!is_int($index)) {
            throw new InvalidArgumentException('Index must be an integer');
        }

        if ($index < 0) {
            throw new InvalidArgumentException('Index must be a non-negative integer');
        }

        return $index < $this->count();
    }
public function indexExists($index)
    {
        if (!is_int($index)) {
            throw new InvalidArgumentException('Index must be an integer');
        }

        if ($index < 0) {
            throw new InvalidArgumentException('Index must be a non-negative integer');
        }

        return $index < $this->count();
    }
{@inheritdoc}