code: func addDefaultTargetFilter(chCtx context.Channel, ft filter.EndpointType) RequestOption {
  	return func(ctx context.Client, o *requestOptions) error {
  		if len(o.Targets) == 0 && o.TargetFilter == nil {
  			return WithTargetFilter(filter.NewEndpointFilter(chCtx, ft))(ctx, o)
  		}
  		return nil
  	}
  }
docs: // addDefaultTargetFilter adds default target filter if target filter is not specified