func (t *Tree) ToString() []byte {
sb := util.StringBuilder{}
sb.Int(len(t.nodes))
sb.Write("\n")
for i, node := range t.nodes {
sb.Int(i)
sb.Write("\t")
sb.Int(node.left)
sb.Write("\t")
sb.Int(node.right)
sb.Write("\t")
sb.Int(node.depth)
sb.Write("\t")
sb.WriteBytes(node.prediction.ToString())
sb.Write("\t")
sb.Int(node.sample_count)
sb.Write("\t")
sb.Int64(node.feature_split.Id)
sb.Write("\t")
sb.Float(node.feature_split.Value)
sb.Write("\n")
}
return sb.Bytes()
}