nested
fun <T : SubDocument> nested( name: String?, factory: (DocSourceField) -> T, dynamic: Dynamic? = null, params: Params = Params()): SubDocument.UnboundSubDocument<T>
fun <T : SubDocument> nested( factory: (DocSourceField) -> T, dynamic: Dynamic? = null, params: Params = Params()): SubDocument.UnboundSubDocument<T>