Pinq\Queries\Builders\ExpressionInterpreter::getOptionalArgumentValueAt PHP Method

    protected final function getOptionalArgumentValueAt($index, O\MethodCallExpression $methodExpression, $default = null)
    {
        $argumentExpression = $this->getOptionalArgumentAt($index, $methodExpression);
        if ($argumentExpression === null) {
            return $default;
        }
        return $argumentExpression->evaluate($this->evaluationContext);
    }