public class ChartDefinitionBase
{
    public ChartDefinitionBase(ObjectId id, IDictionary<ISite, IExample> examples)
    {
        ObjectId = id;
        Examples = examples;
    }

    [BsonIgnoreIfDefault]
    [BsonId(IdGenerator = typeof(ObjectIdGenerator))]
    public ObjectId ObjectId { get; private set; }

    [BsonDictionaryOptions(DictionaryRepresentation.ArrayOfDocuments)]
    public IDictionary<ISite, IExample> Examples{ get; private set; }
}