public static JavaRDD<List<List<Writable>>> zeroMeanUnitVarianceSequence(Schema schema,JavaRDD<List<List<Writable>>> sequence){
  return zeroMeanUnitVarianceSequence(schema,sequence,null);
}

public static JavaRDD < List < List < Writable > > > zeroMeanUnitVarianceSequence ( Schema schema , JavaRDD < List < List < Writable > > > sequence ) { return zeroMeanUnitVarianceSequence ( schema , sequence , null ) ; }
normalize the sequence by zero mean unit variance
