def delete_subscriptions(self):
        """Remove all subscriptions.

        Warning: This could be slow for large numbers of connected devices.
        If possible, explicitly delete subscriptions known to have been created.

        :returns: None
        """
        warnings.warn('This could be slow for large numbers of connected devices.'
                      'If possible, explicitly delete subscriptions known to have been created.')
        for device in self.list_connected_devices():
            try:
                self.delete_device_subscriptions(device_id=device.id)
            except CloudApiException as e:
                LOG.warning('failed to remove subscription for %s: %s', device.id, e)
                continue