code: @RequiresPermission(ACCESS_WIFI_STATE)
    public static Observable<WifiSignalLevel> observeWifiSignalLevel(final Context context) {
      return observeWifiSignalLevel(context, WifiSignalLevel.getMaxLevel()).map(
          new Function<Integer, WifiSignalLevel>() {
            @Override public WifiSignalLevel apply(Integer level) throws Exception {
              return WifiSignalLevel.fromLevel(level);
            }
          });
    }
docs: Observes WiFi signal level with predefined max num levels.
  Returns WiFi signal level as enum with information about current level
  
  @param context Context of the activity or an application
  @return WifiSignalLevel as an enum