return backingEntry.getValue().size();
            }
          };
        }
      };
    }

    @Override
    public Spliterator<K> spliterator() {
      return CollectSpliterators.map(multimap.entries().spliterator(), Map.Entry::getKey);
    }

    @Override
    public void forEach(Consumer<? super K> consumer) {
      checkNotNull(consumer);