@Override
			public void post(@NonNull final Runnable r) {
				if (handler != null) handler.post(r);
				else r.run();
			}
Sets the handler that will be used to invoke callbacks. By default, the handler set in
{@link BleManager} will be used.
<p>
If set to null, the callbacks will be invoked immediately on the BLE looper.

@param handler The handler to invoke callbacks for this request.
@return The request.
@apiNote Since version 2.4.0 this method accepts null as parameter.
ble/src/main/java/no/nordicsemi/android/ble/Request.java