*/
  @J2ktIncompatible // serialization
  static class SerializedForm<K, V> implements Serializable {
    // This object retains references to collections returned by keySet() and value(). This saves
    // bytes when the both the map and its keySet or value collection are written to the same
    // instance of ObjectOutputStream.

            "four", 4,
            "five", 5,
            "six", 6,
            "seven", 7),
        "one",
        1,
        "two",
        2,
        "three",
        3,
        "four",
        4,
        "five",
        5,
        "six",
        6,
        "seven",
        7);
    assertMapEquals(
        ImmutableMap.of(
            "one", 1,

       *
       * Accordingly, we have it annotated as returning `Enumeration<? extends Object>` in our
       * prototype checker's JDK. However, the checker still sees the return type as plain
       * `Enumeration<?>`, probably because of one of the following two bugs (and maybe those two
       * bugs are themselves just symptoms of the same underlying problem):
       *