code: public void setPreferences(OperaPreferences newPreferences) {
      if (!(newPreferences instanceof OperaFilePreferences)) {
        OperaFilePreferences convertedPreferences = new OperaFilePreferences(preferenceFile);
        convertedPreferences.merge(newPreferences);
        preferences = convertedPreferences;
      } else {
        preferences = newPreferences;
      }
    }
docs: Replaces the preferences in the profile with the given preferences.
  
  @param newPreferences the new preferences to populate the profile with