code: public StringBuffer format(Object keyword, StringBuffer toAppendTo,
              FieldPosition pos) {
          if (keyword instanceof String) {
              toAppendTo.append(format( (String)keyword));
          }else{
              throw new IllegalArgumentException("'" + keyword + "' is not a String");
          }
          return toAppendTo;
      }
docs: Selects the phrase for the given keyword.
  and appends the formatted message to the given <code>StringBuffer</code>.
  @param keyword a phrase selection keyword.
  @param toAppendTo the selected phrase will be appended to this
  <code>StringBuffer</code>.
  @param pos will be ignored by this method.
  @throws IllegalArgumentException when the given keyword is not a String
  or not a "pattern identifier"
  @return the string buffer passed in as toAppendTo, with formatted text
  appended.