public IEnumerable <T> GetKingMarkers <T>(Color color, params MarkerType[] types) where T : IMarker => m_markings.GetKingMarkers <T>(color, types);
public IEnumerable <T> GetKingMarkers <T>(Color color, params MarkerType[] types) where T : IMarker => KingLocations.ContainsKey(color) ? GetMarkers <T>(KingLocations[color], types) : Enumerable.Empty <T>();