This method is used to initialize multipart upload to get uploadId. This uploadId will be used on copy part, complete, abort multi part operations.
String initializeMultiPartUpload(String awsLocation)
awsLocation: The name of key to be uploaded as file location. You can get this value from the fileLocation of UploadRequestInfo object.
Return Value: The method will return the uploadId as a String.

Example code:
String uploadId = cg.SDriveTools.initializeMultiPartUpload(uploadRequestInfos.fileLocation);