question: @ Override public Map < Long , String > mapping ( Map < Long , String > originalDatapoints , List < String > constants ) { SystemAssert . requireArgument ( constants != null , "This transform needs constants" ) ; SystemAssert . requireArgument ( constants . size ( ) == 2 , "This transform must provide exactly 2 constants." ) ; this . threshold = getOffsetInSeconds ( constants . get ( 0 ) ) * 1000 ; this . connectDistance = getOffsetInSeconds ( constants . get ( 1 ) ) * 1000 ; Map < Long , String > resultMetric = new TreeMap < Long , String > ( ) ; this . keyList = new ArrayList < Long > ( ) ; this . resultKeyList = new ArrayList < Long > ( ) ; keyList . addAll ( originalDatapoints . keySet ( ) ) ; Collections . sort ( keyList ) ; if ( keyList . size ( ) > 0 ) { connect ( 0 , new ArrayList < > ( Arrays . asList ( keyList . get ( 0 ) ) ) ) ; } for ( Long resultKey : resultKeyList ) { resultMetric . put ( resultKey , originalDatapoints . get ( resultKey ) ) ; } return resultMetric ; }
target:  mapping method implementation<br> This is the start point of this transform. It firstly verifies if all inputs are legal, then it crawls forward on this series and collects every qualified adjacent datapoints along the way.