code: func CallFlowByID(client *messagebird.Client, id string) (*CallFlow, error) {
  	var data struct {
  		Data []CallFlow `json:"data"`
  	}
  	if err := client.Request(&data, http.MethodGet, apiRoot+"/call-flows/"+id, nil); err != nil {
  		return nil, err
  	}
  	return &data.Data[0], nil
  }
docs: // CallFlowByID fetches a callflow by it's ID.
  //
  // An error is returned if no such call flow exists or is accessible.