How to use the pywemo.discover_devices function in pywemo

def scan_power_switches(callback=None, **kwargs):
    for device in pywemo.discover_devices():
      yield terrariumPowerSwitch(md5((terrariumPowerSwitchWeMo.TYPE + device.serialnumber).encode()).hexdigest(),
                                 terrariumPowerSwitchWeMo.TYPE,
                                 device.host,
                                 device.name,
                                 None,
                                 callback)

try:
                device = pywemo.discovery.device_from_description(url, None)
            except (
                requests.exceptions.ConnectionError,
                requests.exceptions.Timeout,
            ) as err:
                _LOGGER.error("Unable to access WeMo at %s (%s)", url, err)
                continue

            if not [d[1] for d in devices if d[1].serialnumber == device.serialnumber]:
                devices.append((url, device))

        if config.get(DOMAIN, {}).get(CONF_DISCOVERY, DEFAULT_DISCOVERY):
            _LOGGER.debug("Scanning network for WeMo devices...")
            for device in pywemo.discover_devices():
                if not [
                    d[1] for d in devices if d[1].serialnumber == device.serialnumber
                ]:
                    devices.append((setup_url_for_device(device), device))

        for url, device in devices:
            _LOGGER.debug("Adding WeMo device at %s:%i", device.host, device.port)

            discovery_info = {
                "model_name": device.model_name,
                "serial": device.serialnumber,
                "mac_address": device.mac,
                "ssdp_description": url,
            }

            discovery_dispatch(SERVICE_WEMO, discovery_info)

def _scan_once(self):
    devices = pywemo.discover_devices()

    logging.info('Found %d wemo devices.', len(devices))

    for device in devices:
      device_exists = device.serialnumber in self._devices
      self._devices[device.serialnumber] = device

      state = device.get_state()
      serialnumber = device.serialnumber
      state_changed = state != self._state_cache.get(serialnumber, None)
      self._state_cache[serialnumber] = state

      details = {
          'serial_number': serialnumber,
          'model': device.model,
          'name': device.name,

continue

            try:
                device = pywemo.discovery.device_from_description(url, None)
            except (requests.exceptions.ConnectionError,
                    requests.exceptions.Timeout) as err:
                _LOGGER.error('Unable to access WeMo at %s (%s)', url, err)
                continue

            if not [d[1] for d in devices
                    if d[1].serialnumber == device.serialnumber]:
                devices.append((url, device))

        if config.get(DOMAIN, {}).get(CONF_DISCOVERY):
            _LOGGER.debug("Scanning network for WeMo devices...")
            for device in pywemo.discover_devices():
                if not [d[1] for d in devices
                        if d[1].serialnumber == device.serialnumber]:
                    devices.append((setup_url_for_device(device),
                                    device))

        for url, device in devices:
            _LOGGER.debug('Adding WeMo device at %s:%i',
                          device.host, device.port)

            discovery_info = {
                'device_type': device.__class__.__name__,
                'serial': device.serialnumber,
                'mac_address': device.mac,
                'ssdp_description': url,
            }

async def _async_has_devices(hass):
    """Return if there are devices that can be discovered."""
    return bool(await hass.async_add_executor_job(pywemo.discover_devices))