//-----------------------------------------------------------------------------------------------------------------------------------------------------
 public TypeMetadataCache(
     DataObjectConventions dataObjectConventions,
     IRelationalMappingConvention relationalMappingConvention,
     IEnumerable<MixinRegistration> mixinRegistrations)
 {
     _dataObjectConventions = dataObjectConventions;
     _relationalMappingConvention = relationalMappingConvention;
     _mixinsByPrimaryContract = mixinRegistrations.GroupBy(r => r.TargetContract).ToDictionary(g => g.Key, g => g.ToArray());
 }
 //-----------------------------------------------------------------------------------------------------------------------------------------------------
 public TypeMetadataCache(
     DataObjectConventions dataObjectConventions, 
     IRelationalMappingConvention relationalMappingConvention)
     : this(dataObjectConventions, relationalMappingConvention, mixinRegistrations: new MixinRegistration[0])
 {
 }