public static Builder builder() {
    return new Builder();
  }
@Test(expectedExceptions = NullPointerException.class)
  public void testBuilderNoNullGeneratorThrowExceptions() {
    StreamDataProducer producer = Mockito.mock(StreamDataProducer.class);
    PinotRealtimeSource realtimeSource =
        PinotRealtimeSource.builder().setTopic("mytopic").setProducer(producer).build();
  }