code: func (s *PresenceService) GetTunnelConnections(clusterName string, opts ...services.MarshalOption) ([]services.TunnelConnection, error) {
  	if clusterName == "" {
  		return nil, trace.BadParameter("missing cluster name")
  	}
  	startKey := backend.Key(tunnelConnectionsPrefix, clusterName)
  	result, err := s.GetRange(context.TODO(), startKey, backend.RangeEnd(startKey), backend.NoLimit)
  	if err != nil {
  		return nil, trace.Wrap(err)
  	}
  	conns := make([]services.TunnelConnection, len(result.Items))
  	for i, item := range result.Items {
  		conn, err := services.UnmarshalTunnelConnection(item.Value,
  			services.AddOptions(opts, services.WithResourceID(item.ID), services.WithExpires(item.Expires))...)
  		if err != nil {
  			return nil, trace.Wrap(err)
  		}
  		conns[i] = conn
  	}
  
  	return conns, nil
  }
docs: // GetTunnelConnections returns connections for a trusted cluster