code: @SuppressWarnings("unchecked")
      public Set<RateType> getRateTypes() {
          Set<RateType> result = get(KEY_RATE_TYPES, Set.class);
          if (result == null) {
              return Collections.emptySet();
          }
          return result;
      }
docs: Get the rate types set.
  
  @return the rate types set, or an empty array, but never null.