docs: function addReverseLookupsForExtendeds (reverseDict, dict) {
    Object.keys(dict).forEach(function (key) {
      let pair = dict[key]
      let quality = pair[0]
      let extendedsArr = pair[1]
      extendedsArr.forEach(function (element) {
        reverseDict[element] = {
          quality: quality,
          extended: key
        }
      })
    })
  }