normalize(nodes) {
    if (typeof nodes !== 'object') {
      return nodes
    }

    nodes = nodes.filter(i => i !== '')

    if (typeof nodes[0] === 'string') {
      let firstNode = nodes[0].trim()

      if (
        firstNode.includes(':') ||
        firstNode === 'selector' ||
        firstNode === 'not selector'
      ) {
        return [brackets.stringify(nodes)]
      }
    }
    return nodes.map(i => this.normalize(i))
  }
Compress value functions into a string nodes