locationSetID(locationSet) {
    let locationSetID;
    try {
      locationSetID = _loco.validateLocationSet(locationSet).id;
    } catch {
      locationSetID = '+[Q2]';  // the world
    }
    return locationSetID;
  }
locationSetID
Returns a locationSetID for a given locationSet (fallback to `+[Q2]`, world)
(The locationSet doesn't necessarily need to be resolved to compute its `id`)

@param  `locationSet`  A locationSet Object, e.g. `{ include: ['us'] }`
@return  String locationSetID, e.g. `+[Q30]`