public static MockProjectElementLinkRemoter ExportElement(this ProjectCollectionLinker exporter, ProjectElement xml)
        {
            if (xml == null)
            {
                return(null);
            }

            var implType = xml.GetType();

            if (knownTypes.TryGetValue(implType, out var factory))
            {
                return(factory(exporter, xml));
            }

            factory = NotImplemented;

            foreach (var t in canonicalTypes)
            {
                if (t.Checker(xml))
                {
                    factory = t.ExportFactory;
                    break;
                }
            }

            lock (knownTypes)
            {
                var newKnown = new Dictionary <Type, ExporterFactory>(knownTypes);
                newKnown[implType] = factory;
                knownTypes         = newKnown;
            }

            return(factory(exporter, xml));
        }