docs: def restore(self):
          """Restore snapshotted state."""
          if not self._snapshot:
              return
          yield from self.set_name(self._snapshot['name'])
          yield from self.set_volume(self._snapshot['volume'])
          yield from self.set_muted(self._snapshot['muted'])
          yield from self.set_latency(self._snapshot['latency'])
          self.callback()
          _LOGGER.info('restored snapshot of state of %s', self.friendly_name)