     return mapFromJson(toCollection: &field, map: map)
 }
 
-private func mapToJson<T, U: Mapping, V: Sequence>(
-    _ json: JSONValue,
+private func map<T, U: Mapping, V: Sequence>(
+    to json: JSONValue,
     fromField field: V,
     viaKey key: Keypath,
     mapping: U)

    return json
}

private func mapToJson<T, U: Mapping>(_ json: JSONValue, fromField field: T?, viaKey key: Keypath, mapping: U) throws -> JSONValue where U.MappedObject == T {
    var json = json
    
    guard let field = field else {


// MARK: - To JSON

private func map<T: JSONable>(to json: JSONValue, fromField field: T?, viaKey key: JSONKeypath) -> JSONValue where T == T.ConversionType {
    var json = json
    
    if let field = field {
