docs: @Override
      public Object map(Object sourceEnumerable, Function mapFunction, boolean filterNulls) {
          Validate.argumentIsNotNull(mapFunction);
  
          Multimap sourceMultimap = toNotNullMultimap(sourceEnumerable);
          Multimap targetMultimap = ArrayListMultimap.create();
  
          MapType.mapEntrySet(sourceMultimap.entries(), mapFunction, (k,v) -> targetMultimap.put(k,v), filterNulls);
  
          return targetMultimap;
      }