code: static <K, V> ImmutableSetMultimap<K, V> fromMapEntries(
        Collection<? extends Map.Entry<? extends K, ? extends Collection<? extends V>>> mapEntries,
        @Nullable Comparator<? super V> valueComparator) {
      if (mapEntries.isEmpty()) {
        return of();
      }
      ImmutableMap.Builder<K, ImmutableSet<V>> builder =
          new ImmutableMap.Builder<>(mapEntries.size());
      int size = 0;
  
      for (Entry<? extends K, ? extends Collection<? extends V>> entry : mapEntries) {
        K key = entry.getKey();
        Collection<? extends V> values = entry.getValue();
        ImmutableSet<V> set = valueSet(valueComparator, values);
        if (!set.isEmpty()) {
          builder.put(key, set);
          size += set.size();
        }
      }
  
      return new ImmutableSetMultimap<>(builder.build(), size, valueComparator);
    }
docs: Creates an ImmutableSetMultimap from an asMap.entrySet.