public function setOpeningBalanceClass($openingBalanceClass)
    {
        if (!is_callable($openingBalanceClass) && !class_exists($openingBalanceClass)) {
            throw new \InvalidArgumentException('$openingBalanceClass must be a valid classname or a PHP callable');
        }

        $this->openingBalanceClass = $openingBalanceClass;
        return $this;
    }