public synchronized AppleSignalInterface makeSignalInterface(
    TokensAndUrlAuthData authData,
    AppCredentials appCredentials,
    Monitor monitor) {

    Preconditions.checkNotNull(authData, ERROR_MESSAGE, "authData");
    Preconditions.checkNotNull(appCredentials, ERROR_MESSAGE, "appCredentials");
    Preconditions.checkNotNull(monitor, ERROR_MESSAGE, "monitor");

    return new AppleSignalInterface(authData, appCredentials, monitor);
  }
The Factory class that creates the Apple Import Extensions.
extensions/data-transfer/portability-data-transfer-apple/src/main/java/org/datatransferproject/datatransfer/apple/AppleInterfaceFactory.java