public List<String> getTransformersNames() {
    return transformers.stream().map(t -> t.getTransformer().getClass().getName()).collect(Collectors.toList());
  }
@Test
  public void testGetTransformersNames() {
    Transformer t1 = (jsc, sparkSession, dataset, properties) -> dataset.withColumnRenamed("foo", "bar");
    Transformer t2 = (jsc, sparkSession, dataset, properties) -> dataset.withColumn("bar", dataset.col("bar").cast(IntegerType));
    ChainedTransformer transformer = new ChainedTransformer(Arrays.asList(t1, t2));
    List<String> classNames = transformer.getTransformersNames();
    assertEquals(t1.getClass().getName(), classNames.get(0));
    assertEquals(t2.getClass().getName(), classNames.get(1));
  }