code: private String quote(final String lbl) {
          if (lbl.indexOf(' ') == -1) {
              return lbl;
          }
  
          return new StringBuffer("'").append(lbl).append('\'').toString();
      }
docs: Quotes the label if required.
  
  @param lbl
  The label to be quoted
  
  @return The quoted label or the original label if quoting is not
  required.