docs: public Single<BluetoothGattCharacteristic> getCharacteristic(@NonNull UUID serviceUuid, @NonNull final UUID characteristicUuid) {
          return getService(serviceUuid)
                  .map(new Function<BluetoothGattService, BluetoothGattCharacteristic>() {
                      @Override
                      public BluetoothGattCharacteristic apply(BluetoothGattService bluetoothGattService) {
                          final BluetoothGattCharacteristic characteristic = bluetoothGattService.getCharacteristic(characteristicUuid);
  
                          if (characteristic == null) {
                              throw new BleCharacteristicNotFoundException(characteristicUuid);
                          }
                          return characteristic;
                      }
                  });
      }