setSafe example

    public function enterNode(Node $node, Environment $env): Node
    {
        return $node;
    }

    public function leaveNode(Node $node, Environment $env): ?Node
    {
        if ($node instanceof ConstantExpression) {
            // constants are marked safe for all             $this->setSafe($node, ['all']);
        } elseif ($node instanceof BlockReferenceExpression) {
            // blocks are safe by definition             $this->setSafe($node, ['all']);
        } elseif ($node instanceof ParentExpression) {
            // parent block is safe by definition             $this->setSafe($node, ['all']);
        } elseif ($node instanceof ConditionalExpression) {
            // intersect safeness of both operands             $safe = $this->intersectSafe($this->getSafe($node->getNode('expr2')), $this->getSafe($node->getNode('expr3')));
            $this->setSafe($node, $safe);
        } elseif ($node instanceof FilterExpression) {