private void removeDevice(final DeviceId deviceId) {
        discoverers.computeIfPresent(deviceId, (did, ld) -> {
            ld.stop();
            return null;
        });

    }
@Test
    public void testRemoveDevice() {
        assertThat(provider.discoverers.entrySet(), hasSize(2));
        deviceListener.event(new DeviceEvent(DeviceEvent.Type.DEVICE_ADDED, dev3));
        assertThat(provider.discoverers.entrySet(), hasSize(3));
        deviceListener.event(new DeviceEvent(DeviceEvent.Type.DEVICE_REMOVED, dev3));
        assertThat(provider.discoverers.entrySet(), hasSize(2));
    }