public static <V> TimestampedValue<V> atMinimumTimestamp(V value) {
    return of(value, BoundedWindow.TIMESTAMP_MIN_VALUE);
  }
@Test
  public void testAtMinimumTimestamp() {
    TimestampedValue<String> tsv = TimestampedValue.atMinimumTimestamp("foobar");
    assertEquals(BoundedWindow.TIMESTAMP_MIN_VALUE, tsv.getTimestamp());
  }