private static Single<BluetoothGattCharacteristic> getCharacteristic(UUID characteristicUuid, RxBleConnection rxBleConnection) {
        return rxBleConnection
                .discoverServices() // when connected discover services
                .flatMap(services -> services.getCharacteristic(characteristicUuid));
    }
Presenter class for {@link AdvancedCharacteristicOperationExampleActivity}. Prepares the logic for the activity using passed
{@link Observable}s. Contains only static methods to show a purely reactive (stateless) approach.
<p>
The contract of the class is that it subscribes to the passed Observables only if a specific functionality is possible to use.
sample/src/main/java/com/polidea/rxandroidble2/sample/example4_characteristic/advanced/Presenter.java