@NonNull
	public Request then(@NonNull final AfterCallback callback) {
		this.afterCallback = callback;
		return this;
	}
Sets a callback that will be executed when the request has been processed, no matter
the request result.
<p>
Set {@link #done(SuccessCallback)} or {@link #fail(FailCallback)} if you need a callback
called in a specific situation.
<p>
This request will not be called if the {@link BluetoothDevice} was not set. Instead,
{@link InvalidRequestCallback} will be called.

@param callback the callback.
@return The request.
@see #invalid(InvalidRequestCallback)
ble/src/main/java/no/nordicsemi/android/ble/Request.java