public BoundedReadFromUnboundedSource<T> withMaxNumRecords(long maxNumRecords) {
    return new BoundedReadFromUnboundedSource<>(source, maxNumRecords, maxReadTime);
  }
@Test
  public void testForwardsDisplayData() {
    TestCountingSource src =
        new TestCountingSource(1234) {
          @Override
          public void populateDisplayData(DisplayData.Builder builder) {
            builder.add(DisplayData.item("foo", "bar"));
          }
        };

    BoundedReadFromUnboundedSource<KV<Integer, Integer>> read = Read.from(src).withMaxNumRecords(5);
    assertThat(DisplayData.from(read), includesDisplayDataFor("source", src));
  }