private String setupApacheFopConfiguration(FOSettings settings) throws Docx4JException {

    String ret = settings.getApacheFopConfiguration();
    WordprocessingMLPackage wmlPackage = (WordprocessingMLPackage) settings.getWmlPackage();
    if (ret == null) {
      ret =
          FopConfigUtil.createDefaultConfiguration(
              wmlPackage.getFontMapper(), wmlPackage.getMainDocumentPart().fontsInUse());
    }
    return ret;
  }