table.put("three", 'a', 3);
      table.put("four", 'b', 4);
      return table.column('a');
    }
  }

  private abstract static class MapMapTests
      extends MapInterfaceTest<String, Map<Integer, Character>> {

    MapMapTests(
        boolean allowsNullValues,
        boolean supportsRemove,
        boolean supportsClear,
        boolean supportsIteratorRemove) {