protected override IEnumerable <string> GetPerInstanceColumnsToSave(RoleMappedSchema schema)
{
Host.CheckValue(schema, nameof(schema));
Host.CheckValue(schema.Label, nameof(schema), "Data must contain a label column");
Host.CheckValue(schema.Group, nameof(schema), "Data must contain a group column");
// The ranking evaluator outputs the label, group key and score columns.
yield return(schema.Group.Name);
yield return(schema.Label.Name);
var scoreInfo = EvaluateUtils.GetScoreColumnInfo(Host, schema.Schema, ScoreCol, nameof(Arguments.ScoreColumn),
MetadataUtils.Const.ScoreColumnKind.Ranking);
yield return(scoreInfo.Name);
// Return the output columns.
yield return(RankerPerInstanceTransform.Ndcg);
yield return(RankerPerInstanceTransform.Dcg);
yield return(RankerPerInstanceTransform.MaxDcg);
}
