code: public static synchronized WonderPushChannel getChannel(String channelId) {
          try {
              WonderPushChannel rtn = sChannels.get(channelId);
              if (rtn != null) {
                  try {
                      rtn = (WonderPushChannel) rtn.clone();
                  } catch (CloneNotSupportedException ex) {
                      Log.e(WonderPush.TAG, "Unexpected error while cloning gotten channel " + rtn, ex);
                      return null;
                  }
              }
              return rtn;
          } catch (Exception ex) {
              Log.e(WonderPush.TAG, "Unexpected error while getting channel " + channelId, ex);
              return null;
          }
      }
docs: Get a channel.
  @param channelId The identifier of the channel to get.
  @return The channel, if it has previously been created using this class,
  {@code null} otherwise, in particular if an Android {@link android.app.NotificationChannel}
  exists but has not been registered with this class.