}
        }
        // check unrelated items in all other groups
        for (int unrelatedGroupNumber = 0;
            unrelatedGroupNumber < groups.size();
            unrelatedGroupNumber++) {
          if (groupNumber != unrelatedGroupNumber) {
            ImmutableList<T> unrelatedGroup = groups.get(unrelatedGroupNumber);
            for (int unrelatedItemNumber = 0;
                unrelatedItemNumber < unrelatedGroup.size();