protected override Delegate GetGetterCore(IChannel ch, IRow input, int iinfo, out Action disposer)
        {
            Host.AssertValueOrNull(ch);
            Host.AssertValue(input);
            Host.Assert(0 <= iinfo && iinfo < Infos.Length);
            disposer = null;

            var getSrc = GetSrcGetter <DvText>(input, iinfo);

            return(_valueMap.GetGetter(getSrc));
        }