docs: public static DiscreteVariable sequence(String name, int size) {
      List<Integer> values = null;
      if (sequenceCache.containsKey(size)) {
        values = sequenceCache.get(size);
      } else {
        values = Lists.newArrayList();
        for (int i = 0; i < size; i++) {
          values.add(i);
        }
        values = ImmutableList.copyOf(values);
        sequenceCache.put(size, values);
      }
      
      return new DiscreteVariable(name, values);
    }