previous (focus) {
    if (this.results) {
      const max = this.results.length - 1
      let index = this.resultIndex !== null ? this.resultIndex - 1 : max
      if (index < 0) {
        index = max
      }
      this._setActiveResult(index, focus)
    }
  }
Go to the prevous search result
@param {boolean} [focus]   If true, focus will be set to the next result
                           focus is false by default.