import java.util.Random;
import static water.util.RandomUtils.getRNG;
public class ASTKFold extends ASTPrim {
@Override public int nargs() { return 1+3; } // (kfold_column x nfolds seed)
@Override String str() { return "kfold_column"; }
<BUG>@Override ValFrame apply( Env env, Env.StackHelp stk, AST asts[] ) {
Vec foldVec = stk.track(asts[1].exec(env)).getFrame().anyVec().makeZero();
int nfolds = (int)asts[2].exec(env).getNum();
long seed  = (long)asts[3].exec(env).getNum();
return new ValFrame(new Frame(kfoldColumn(foldVec,nfolds,seed==-1?new Random().nextLong():seed)));
}</BUG>
public static Vec kfoldColumn(Vec v, final int nfolds, final long seed) {

import java.util.Random;
import static water.util.RandomUtils.getRNG;
public class ASTKFold extends ASTPrim {
@Override public int nargs() { return 1+3; } // (kfold_column x nfolds seed)
@Override String str() { return "kfold_column"; }
public static Vec kfoldColumn(Vec v, final int nfolds, final long seed) {
