* only contain entries which are already present in the cache.
   *
   * @since 11.0
   */
  /*
   * <? extends Object> is mostly the same as <?> to plain Java. But to nullness checkers, they
   * differ: <? extends Object> means "non-null types," while <?> means "all types."
   */
  ImmutableMap<K, V> getAllPresent(Iterable<? extends Object> keys);

  /**

        .addEqualityGroup(
            MediaType.create("text", "plain"),
            MediaType.create("TEXT", "PLAIN"),
            MediaType.parse("text/plain"),
            MediaType.parse("TEXT/PLAIN"),
            MediaType.parse("text /plain"),
            MediaType.parse("TEXT/ plain"),
            MediaType.parse("text / plain"),
            MediaType.create("text", "plain").withParameter("a", "1").withoutParameters())

        .addEqualityGroup(
            MediaType.create("text", "plain"),
            MediaType.create("TEXT", "PLAIN"),
            MediaType.parse("text/plain"),
            MediaType.parse("TEXT/PLAIN"),
            MediaType.parse("text /plain"),
            MediaType.parse("TEXT/ plain"),
            MediaType.parse("text / plain"),
            MediaType.create("text", "plain").withParameter("a", "1").withoutParameters())

   * returns. This method may be useful when testing the garbage collection mechanism itself, or
   * inhibiting a spontaneous GC initiation in subsequent code.
   *
   * <p>In contrast, a plain call to {@link java.lang.System#gc()} does not ensure finalization
   * processing and may run concurrently, for example, if the JVM flag {@code
   * -XX:+ExplicitGCInvokesConcurrent} is used.
   *

  }

  static class NonTerminalImmutableMapEntry<K, V> extends ImmutableMapEntry<K, V> {
    /*
     * Yes, we sometimes set nextInKeyBucket to null, even for this "non-terminal" entry. We don't
     * do that with a plain NonTerminalImmutableMapEntry, but we do it with the BiMap-specific
     * subclass below. That's because the Entry might be non-terminal in the key bucket but terminal
     * in the value bucket (or vice versa).
     */

   * of the same class. For example, if sublists of {@code MyList} instances were serializable,
   * those sublists might implement a private {@code MySubList} type but serialize as a plain {@code
   * MyList} to save space. So long as {@code MyList} has all the public supertypes of {@code
   * MySubList}, this is safe. For these cases, for which {@code reserializeAndAssert} is too
   * strict, use {@link #reserialize}.

     *
     * Unfortunately, we don't distinguish between these two cases in our public API: Joiner.on(...)
     * and Joiner.on(...).useForNull(...) both declare the same return type: plain Joiner. To ensure
     * that users *can* pass null arguments to Joiner, we annotate it as if it always tolerates null
     * inputs, rather than as if it never tolerates them.
     *

           * non-null Entry objects (Entry objects that might contain null values but are not
           * themselves null), so we can treat it as a plain `Object[]`.
           */
          @SuppressWarnings("nullness")
          Object[] result = standardToArray();
          return result;
        }

        @Override

       *
       * (And I don't believe there's any situation in which we call x.combine(y) when x is a plain
       * ImmutableSet.Builder but y is an ImmutableSortedSet.Builder (or vice versa). Certainly
       * ImmutableSortedSet.Builder.combine() is written as if its argument will never be a plain
       * ImmutableSet.Builder: It casts immediately to ImmutableSortedSet.Builder.)
       */
      copyIfNecessary();

   * of the same class. For example, if sublists of {@code MyList} instances were serializable,
   * those sublists might implement a private {@code MySubList} type but serialize as a plain {@code
   * MyList} to save space. So long as {@code MyList} has all the public supertypes of {@code
   * MySubList}, this is safe. For these cases, for which {@code reserializeAndAssert} is too
   * strict, use {@link #reserialize}.