docs: public static <K, V> ImmutableBiMap<K, V> copyOf(
        Map<? extends K, ? extends V> map) {
      if (map instanceof ImmutableBiMap) {
        @SuppressWarnings("unchecked") // safe since map is not writable
        ImmutableBiMap<K, V> bimap = (ImmutableBiMap<K, V>) map;
        // TODO(user): if we need to make a copy of a BiMap because the
        // forward map is a view, don't make a copy of the non-view delegate map
        if (!bimap.isPartialView()) {
          return bimap;
        }
      }
      return copyOf(map.entrySet());
    }