code: func (s *PresenceService) GetTunnelConnection(clusterName, connectionName string, opts ...services.MarshalOption) (services.TunnelConnection, error) {
  	item, err := s.Get(context.TODO(), backend.Key(tunnelConnectionsPrefix, clusterName, connectionName))
  	if err != nil {
  		if trace.IsNotFound(err) {
  			return nil, trace.NotFound("trusted cluster connection %q is not found", connectionName)
  		}
  		return nil, trace.Wrap(err)
  	}
  	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)
  	}
  	return conn, nil
  }
docs: // GetTunnelConnection returns connection by cluster name and connection name