} catch (Exception e) {
                throw new RuntimeException(e);
            }
        }

        private <T> Set<T> concat(Set<T> set, T elem) {
            Set<T> newSet = new HashSet<>(set);
            newSet.add(elem);
            return newSet;
        }

        @SuppressWarnings("checkstyle:parameternumber")
        private InterimResult build(