IEnumerable<IConversion> Combination(INavigator navigator, IConversion startFeature = null)
{
var startType = Source;
if(startFeature != null)
startType = navigator.End(startFeature);
foreach(var feature in AllFeatures.Where(feature => navigator.Start(feature) == startType))
{
var destination = navigator.End(feature);
if(_foundTypes.Contains(destination))
continue;
_foundTypes.Add(destination);
var newFeature = navigator.Combine(startFeature, feature);
if(newFeature == null)
continue;
yield return newFeature;
_newFeatures.Add(newFeature);
}
}