code: func (mj *Client) GetData(mdr *DataRequest, res interface{}, options ...RequestOptions) (err error) {
  	url := buildDataURL(mj.apiBase, mdr)
  	req, err := createRequest("GET", url, nil, nil, options...)
  	if err != nil {
  		return err
  	}
  
  	_, _, err = mj.httpClient.Send(req).Read(res).Call()
  	return err
  }
docs: // GetData issues a GET to view a resource specifying an id
  // and stores the result in the value pointed to by res.
  // Filters can be add via functional options.
  // Without an specified SourceTypeID in MailjetDataRequest, it is the same as ListData.