Set staging bucket prefix
gcva_bucket_set(stagingBucket)The The Cloud Storage location where the training data is to be written to. In the given directory a new directory is created with name: dataset-<dataset-id>-<annotation-type>-<timestamp-of-training-call> where timestamp is in YYYY-MM-DDThh:mm:ss.sssZ ISO-8601 format. All training input data is written into that directory. If the uri doesn't end with '/', a '/' will be automatically appended. The directory is created if it doesn't exist.