constructor() {
        this.parent = null;
        this.visibilityBlocks = undefined;
        this.nodeVisible = undefined;
        this.rootNode = null;
        this.parsed = null;
    }
The reason why Node is a class and other nodes simply do not extend
from Node (since we're transpiling) is due to this issue:

@see https://github.com/less/less.js/issues/3434