anchor.diff:    void remove(K key, V value) => lookupValues(key).polymorphicRemove(value);
   
     /// Removes associations from [key] to each of [values].
  -  void removeAll(K key, [Iterable<V> values]) =>
  -      values == null
  -          ? lookupValues(key).polymorphicClear()
  -          : lookupValues(key).polymorphicRemoveAll(values);
  +  void removeAll(K key, [Iterable<V> values]) => values == null
  +      ? lookupValues(key).polymorphicClear()
  +      : lookupValues(key).polymorphicRemoveAll(values);
   
     /// Replaces the [key] with a single [value].
  -  void replace(K key, V value) =>
  -      lookupValues(key)
  -        ..polymorphicClear()
  -        ..polymorphicAdd(value);
  +  void replace(K key, V value) => lookupValues(key)
  +    ..polymorphicClear()
  +    ..polymorphicAdd(value);
   
     /// Replaces the [key] with each of the [values].
  -  void replaceAll(K key, Iterable<V> values) =>
  -      lookupValues(key)
  -        ..polymorphicClear()
  -        ..polymorphicAddAll(values);
  +  void replaceAll(K key, Iterable<V> values) => lookupValues(key)
  +    ..polymorphicClear()
  +    ..polymorphicAddAll(values);
   
     /// Removes all values from this multimap.
     void clear() {
  
positive.code:   VS operator [](Object key) => _multimap[key];
  
    @override
    void operator []=(K key, VS value) =>
        _multimap.replaceAll(key, value);
  
    @override
    void clear() => _multimap.clear();
  
negative.code: }
  
  // Internal helper to populate a [multimap] from an [Iterable] of entries.
  void fillFromEntries<K, V, VS extends Iterable<V>>(
      Multimap<K, V, VS> multimap, Iterable<MapEntry<K, V>> entries) {
    for (final entry in entries) {
      multimap.add(entry.key, entry.value);
    }
  