question: public Instances transform ( Instances D ) throws Exception { int L = D . classIndex ( ) ; d = D . numAttributes ( ) - L ; int keep [ ] = A . append ( this . paY , j ) ; Arrays . sort ( keep ) ; int remv [ ] = A . invert ( keep , L ) ; Arrays . sort ( remv ) ; map = new int [ L ] ; for ( int j = 0 ; j < L ; j ++ ) { map [ j ] = Arrays . binarySearch ( keep , j ) ; } Instances D_ = F . remove ( new Instances ( D ) , remv , false ) ; D_ . setClassIndex ( map [ this . j ] ) ; return D_ ; }
target:  Transform - transform dataset D for this node. this.j defines the current node index, e.g., 3 this.paY[] defines parents,            e.g., [1,4] we should remove the rest,             e.g., [0,2,5,...,L-1]