get https://marketplace.walmartapis.com/v3/shipping/labels/carriers//trackings/
Download label by carrier and trackingNo. The response to a successful call contains the tracking number with the PDF or image type based on the media type passed in Accept header. For example, 'Accept'='application/json,application/pdf' will result in PDF media type ,'Accept'='application/json,image/png' as image media type as Accept'='application/json as JSON response.