}

      @Override
      public boolean equals(@Nullable Object obj) {
        return obj instanceof TypeWithDuplicates && ((TypeWithDuplicates) obj).a == a;
      }

      public boolean fullEquals(@Nullable TypeWithDuplicates other) {
        return other != null && a == other.a && b == other.b;
      }
    }

    Collector<TypeWithDuplicates, ?, ImmutableMultiset<TypeWithDuplicates>> collector =