code: func (cli *OpsGenieHeartbeatClient) List(req heartbeat.ListHeartbeatsRequest) (*heartbeat.ListHeartbeatsResponse, error) {
  	req.APIKey = cli.apiKey
  	resp, err := cli.sendRequest(cli.buildGetRequest(listHeartbeatURL, req))
  
  	if resp == nil {
  		return nil, err
  	}
  	defer resp.Body.Close()
  
  	var listHeartbeatsResp heartbeat.ListHeartbeatsResponse
  	if err = resp.Body.FromJsonTo(&listHeartbeatsResp); err != nil {
  		message := "Server response can not be parsed, " + err.Error()
  		logging.Logger().Warn(message)
  		return nil, errors.New(message)
  	}
  
  	return &listHeartbeatsResp, nil
  }
docs: // Deprecated: List method retrieves heartbeats from OpsGenie.