@CanIgnoreReturnValue
  @Override
  public JsonWriter beginArray() throws IOException {
    JsonArray array = new JsonArray();
    put(array);
    stack.add(array);
    return this;
  }
@Test
  public void testBeginArray() throws Exception {
    JsonTreeWriter writer = new JsonTreeWriter();
    assertThat(writer.beginArray()).isEqualTo(writer);
  }