for (Object key : keys) {
          map.put(key, new Object());
        }
        return map;
      };
    }

    static Construction<Set<Object>> setFromElements(Supplier<Set<Object>> mutableSupplier) {
      return elements -> {
        Set<Object> set = mutableSupplier.get();
        set.addAll(elements);
        return set;
      };
    }
  }