How to remove the `SEQ! org.apache.hadoop.io.NullWritable...` header when writing byte to file?

Hi all,
I’m trying to save the booster of a xgboostRegressionModel to Windows Azure Storage Blob (WASB) but got "unknown filesystem protocol wasb://" error as below:

I thought it maybe because that the booster.saveModel function do not support save to wasb at present. So I used saveAsObjectFile to save the booster byte array, but got the following at the top of file:


How can I remove this header from the file?

Thank you so much!!