src/Model/Order.php
public function getModifier($className, $forcecreate = false)
    {
        $calculator = OrderTotalCalculator::create($this);
        return $calculator->getModifier($className, $forcecreate);
    }
public function getModifier($className, $forcecreate = false)
    {
        $calculator = OrderTotalCalculator::create($this);
        return $calculator->getModifier($className, $forcecreate);
    }
This is needed to maintain backwards compatiability with
some subsystems using modifiers. eg discounts