public function process()
    {
        $operands = $this->getOperands();
        $expression = $this->getExpression();

        return new QtiBoolean($operands->containsNull());
    }
public function process()
    {
        $operands = $this->getOperands();
        $expression = $this->getExpression();

        return new QtiBoolean($operands->containsNull());
    }
public function process ( ) { $ operands = $ this -> getOperands ( ) ; $ expression = $ this -> getExpression ( ) ; return new QtiBoolean ( $ operands -> containsNull ( ) ) ; }
Process the IsNullExpression object from the QTI Data Model.

@return boolean Whether the sub-expression is considered to be NULL.
@throws \qtism\runtime\expressions\operators\OperatorProcessingException If something goes wrong.
Process the IsNullExpression object from the QTI Data Model .