* has elapsed after the entry's creation, or the most recent replacement of its value.
   *
   * <p>When {@code duration} is zero, this method hands off to {@link #maximumSize(long)
   * maximumSize}{@code (0)}, ignoring any otherwise-specified maximum size or weight. This can be
   * useful in testing, or to disable caching temporarily without a code change.
   *

     * difference is that calling it with <Foo> won't work when an input Future has a @Nullable
     * type. So why even make that error possible by giving callers the choice?
     *
     * On the other hand, the current signature is consistent with the similar allAsList method. And
     * eventually this method may go away entirely in favor of an API like

   * description of the returned view's behavior.
   *
   * <p><b>Warning:</b> {@code Range}s always represent a range of values using the values' natural
   * ordering. {@code NavigableSet} on the other hand can specify a custom ordering via a {@link
   * Comparator}, which can violate the natural ordering. Using this method (or in general using