question: List < Key > subrecordKeys ( long lowTime , long highTime ) { List < Key > keys = new ArrayList < Key > ( ) ; long lowBucketNumber = bucketNumber ( lowTime ) ; long highBucketNumber = bucketNumber ( highTime ) ; for ( long index = lowBucketNumber ; index <= highBucketNumber ; index += this . bucketSize ) { keys . add ( formSubrecordKey ( index ) ) ; } return keys ; }
target:  creates a list of Keys in the time series