text: class CardListTracker {
    constructor () {
      this.cardLists = []
    }
  
    insideACardList () {
      return this.cardLists.length > 0
    }
  
    getCurrentCardList () {
      return this.cardLists.length === 0
        ? null
        : this.cardLists[this.cardLists.length - 1]
    }
  
    addCardList (cardListId) {
      this.cardLists.push(cardListId)
    }
  
    onRoot () {
      return this.cardLists.length < 2
    }
  
    removeCardList (cardListId) {
      return this.cardLists.pop()
    }
  }
  
  module.exports = new CardListTracker()
  