replace method
      
void
replace(
    
- dynamic multimap
Replaces all elements with elements from a Map, SetMultimap or
BuiltSetMultimap.
Implementation
void replace(dynamic multimap) {
  if (multimap is _BuiltSetMultimap<K, V>) {
    _setOwner(multimap);
  } else if (multimap is Map) {
    _setWithCopyAndCheck(multimap.keys, (k) => multimap[k]);
  } else if (multimap is BuiltSetMultimap) {
    _setWithCopyAndCheck(multimap.keys, (k) => multimap[k]);
  } else {
    _setWithCopyAndCheck(multimap.keys, (k) => multimap[k]);
  }
}