code: public boolean isValidFamily( String theFamily )
      {
  
          // in case they are checking !family
          theFamily = StringUtils.stripStart( theFamily, "!" );
  
          return ( StringUtils.isEmpty( theFamily ) || Os.getValidFamilies().contains( theFamily ) );
      }
docs: Helper method to check if the given family is in the following list:
  <ul>
  <li>dos</li>
  <li>mac</li>
  <li>netware</li>
  <li>os/2</li>
  <li>tandem</li>
  <li>unix</li>
  <li>windows</li>
  <li>win9x</li>
  <li>z/os</li>
  <li>os/400</li>
  </ul>
  Note: '!' is allowed at the beginning of the string and still considered valid.
  
  @param theFamily the family to check.
  @return true if one of the valid families.