ImmutableListMultimap.<String, Character>builder()
            .put("foo", 'f')
            .put("foo", 'o')
            .put("foo", 'o')
            .put("poo", 'p')
            .put("poo", 'o')
            .put("poo", 'o')
            .build();
    assertSame(multimap.inverse(), multimap.inverse());
    assertSame(multimap, multimap.inverse().inverse());
  }

   * in which it will attempt to cancel itself.
   *
   * <p>An example use of this method is to convert a serializable object returned from an RPC into
   * a POJO.
   *
   * <p>This method is similar to {@link java.util.concurrent.CompletableFuture#thenApply} and
   * {@link java.util.concurrent.CompletableFuture#thenApplyAsync}. It can also serve some of the