code: public static String getAtonType(Integer ts) {
  		if (ts == null)
  			return null;
  		if (ts < 0 || ts > 31) {
  			return "unknown code " + ts.intValue();
  		} else {
  			if (ts >= 0 && ts < 5) {
  				return atonTypes[ts];
  			} else if (ts < 20) {
  				return categoryTypes[0] + atonTypes[ts];
  			} else {
  				return categoryTypes[1] + atonTypes[ts];
  			}
  		}
  	}
docs: Returns the AtoN type for given integer. If integer is null then returns
  null.
  
  @param ts
  @return