func (cli *OpsGenieHeartbeatClient) Delete(req heartbeat.DeleteHeartbeatRequest) (*heartbeat.DeleteHeartbeatResponse, error) {
	req.ApiKey = cli.apiKey
	// validate mandatory fields: apiKey, name/id
	if req.ApiKey == "" {
		return nil, errors.New("Api Key is a mandatory field and can not be empty")
	}
	if req.Name == "" && req.Id == "" {
		return nil, errors.New("Either Name or Id field is mandatory and can not be empty")
	}
	if req.Name != "" && req.Id != "" {
		return nil, errors.New("Either Name or Id field should be supplied not both")
	}
	// send the request in a query string
	v, _ := goquery.Values(req)
	var resp *goreq.Response
	var err error
	for i := 0; i < cli.retries; i++ {
		resp, err = cli.buildRequest("DELETE", DELETE_HEARTBEAT_URL+"?"+v.Encode(), nil).Do()
		if err == nil {
			break
		}
		time.Sleep(TIME_SLEEP_BETWEEN_REQUESTS)
	}

	// resp, err := goreq.Request{ Method: "DELETE", Uri: DELETE_HEARTBEAT_URL + "?" + v.Encode(), }.Do()
	if err != nil {
		return nil, errors.New("Can not delete the heart beat, unable to send the request")
	}
	// check for the returning http status, 4xx: client errors, 5xx: server errors
	statusCode := resp.StatusCode
	if statusCode >= 400 && statusCode < 500 {
		return nil, errors.New(fmt.Sprintf("Client error %d occured", statusCode))
	}
	if statusCode >= 500 {
		return nil, errors.New(fmt.Sprintf("Server error %d occured", statusCode))
	}
	// try to parse the returning JSON into the response
	var deleteHeartbeatResp heartbeat.DeleteHeartbeatResponse
	if err = resp.Body.FromJsonTo(&deleteHeartbeatResp); err != nil {
		return nil, errors.New("Server response can not be parsed")
	}
	// parsed successfuly with no errors
	return &deleteHeartbeatResp, nil
}