public static <K, V> Cache<K, V> eternal() {
    return forMaximumBytes(Long.MAX_VALUE);
  }
@Test
  public void testClearableCacheClearing() {
    Cache<String, String> parent = Caches.eternal();
    ClearableCache<String, String> cache = new ClearableCache<>(parent);

    parent.put("untracked", "untrackedValue");
    parent.put("tracked", "parentValue");
    cache.put("tracked", "parentValueNowTracked");
    cache.computeIfAbsent("tracked2", (unused) -> "trackedValue2");
    cache.clear();
    assertNull(parent.peek("tracked"));
    assertNull(parent.peek("tracked2"));
    assertEquals("untrackedValue", parent.peek("untracked"));
  }