code: function getRootNode(node) {
    if (!Node.Type.isFunction(node, 'nthRoot')) {
      throw Error('Expected nthRoot');
    }
  
    return node.args.length === 2 ? node.args[1] : Node.Creator.constant(2);
  }
docs: Given an nthRoot node, will return the root node. The root node is the second child of the nthRoot node, but if one doesn't exist, we assume it's a square root and return 2.