code: @Override
      public StateIdsBuilder append(final String stateToken, final StateRange range) {
          return doAppend(Collections.singletonList(new StateId(stateToken, range)));
      }
docs: Appends the specified state token and range to this instance, returning {@code this}.
  
  @param stateToken The state token to append
  @param range The index range
  @return {@code this}