func (nodev *NodeValue) String() (s string) {
	if nodev.IsLeaf {
		s = fmt.Sprintf("Class: %s", nodev.Class)
	} else {
		s = fmt.Sprintf("(SplitValue: %v)",
			reflect.ValueOf(nodev.SplitV))
	}
	return s
}
String will return the value of node for printable.
package cart
import (
	"fmt"
	"reflect"
)
type NodeValue struct {
	Class string
	SplitAttrName string
	IsLeaf bool
	IsContinu bool
	Size int
	SplitAttrIdx int
	SplitV interface{}
}