code: func (api *Client) SetGroupReadMark(group, ts string) error {
  	return api.SetGroupReadMarkContext(context.Background(), group, ts)
  }
docs: // SetGroupReadMark sets the read mark on a private group
  // Clients should try to avoid making this call too often. When needing to mark a read position, a client should set a
  // timer before making the call. In this way, any further updates needed during the timeout will not generate extra
  // calls (just one per channel). This is useful for when reading scroll-back history, or following a busy live
  // channel. A timeout of 5 seconds is a good starting point. Be sure to flush these calls on shutdown/logout.