code: public <K extends K0, V extends V0> Multimap<K, V> build(
        Multimap<? extends K, ? extends V> multimap) {
      Multimap<K, V> result = build();
      result.putAll(multimap);
      return result;
    }
docs: Returns a {@code Multimap} with the specified implementation, initialized with the entries of
  {@code multimap}.