@Override
  public Writable put(Writable key, Writable value) {
    addToMap(key.getClass());
    addToMap(value.getClass());
    return instance.put(key, value);
  }
@SuppressWarnings("deprecation")
  @Test
  public void testForeignClass() {
    MapWritable inMap = new MapWritable();
    inMap.put(new Text("key"), new UTF8("value"));
    inMap.put(new Text("key2"), new UTF8("value2"));
    MapWritable outMap = new MapWritable(inMap);
    MapWritable copyOfCopy = new MapWritable(outMap);
    assertEquals(1, copyOfCopy.getNewClasses());
  }