private static IRtPureSpan CreatePureSpan(IRtSpanStyle styleProto, string initialText = "")
        {
            var span = AmFactory.Create <RtPureSpan>();

            span.Style = styleProto.CloneTyped();
            span.Text  = initialText;
            return(span);
        }
        private static IRtEmbeddingSpan CreateEmbeddingSpan(IRtSpanStyle styleProto, string embeddingType, string initialSource = "")
        {
            var span = AmFactory.Create <RtEmbeddingSpan>();

            span.Style         = styleProto.CloneTyped();
            span.EmbeddingType = embeddingType;
            span.SourceCode    = initialSource;
            return(span);
        }