open class DefaultContainer<Provider: DataServiceProvider>: DataService<Provider> {
    public override init(provider: Provider) {
        super.init(provider: provider)
        self.provider.metadata = DefaultContainerMetadata.document
    }

    // ...

    open func photos(query: DataQuery = DataQuery()) throws -> Array<Photo> {
        return try Photo.array(from: self.executeQuery(query.from(DefaultContainerMetadata.EntitySets.photos)).entityList())
    }
}