// Can't call with too loose a value:
    // transformEntries(map1, transformer);
    // transformEntries(map4, transformer);
    // transformEntries(map7, transformer);
  }

  public void testTransformEntriesExample() {
    Map<String, Boolean> options = ImmutableMap.of("verbose", true, "sort", false);
    EntryTransformer<String, Boolean, String> flagPrefixer =
        new EntryTransformer<String, Boolean, String>() {