Neos\ContentRepository\Eel\FlowQueryOperations\FilterOperation::evaluateOperator PHP Method

    protected function evaluateOperator($value, $operator, $operand)
    {
        if ($operator === 'instanceof' && $value instanceof NodeInterface) {
            if ($this->operandIsSimpleType($operand)) {
                return $this->handleSimpleTypeOperand($operand, $value);
            } elseif ($operand === NodeInterface::class || $operand === Node::class) {
                return true;
            } else {
                $isOfType = $value->getNodeType()->isOfType($operand[0] === '!' ? substr($operand, 1) : $operand);
                return $operand[0] === '!' ? $isOfType === false : $isOfType;
            }
        } elseif ($operator === '!instanceof' && $value instanceof NodeInterface) {
            return !$this->evaluateOperator($value, 'instanceof', $operand);
        }
        return parent::evaluateOperator($value, $operator, $operand);
    }