docs: public String getComparatorType() {
          StringBuilder sb = new StringBuilder();
          sb.append("CompositeType(");
          sb.append(StringUtils.join(
              Collections2.transform(components, new Function<FieldMapper<?>, String>() {
                  public String apply(FieldMapper<?> input) {
                      return input.serializer.getComparatorType().getTypeName();
                  }
              }),
              ","));
          sb.append(")");
          return sb.toString();
      }