@Override
  public String toString() {
    return MoreObjects.toStringHelper(this)
        .add("innerCoder", innerCoder)
        .add("dict", dict == null ? null : "base64:" + BaseEncoding.base64().encode(dict))
        .add("level", level)
        .toString();
  }
@Test
  public void testToString() throws Exception {
    assertEquals(
        "ZstdCoder{innerCoder=StringUtf8Coder, dict=null, level=0}",
        ZstdCoder.of(StringUtf8Coder.of(), null, 0).toString());
    assertEquals(
        "ZstdCoder{innerCoder=ByteArrayCoder, dict=base64:, level=1}",
        ZstdCoder.of(ByteArrayCoder.of(), new byte[0], 1).toString());
    assertEquals(
        "ZstdCoder{innerCoder=TextualIntegerCoder, dict=base64:AA==, level=2}",
        ZstdCoder.of(TextualIntegerCoder.of(), new byte[1], 2).toString());
  }