*       one with {@link CharSequence#charAt(int)}.
   *   <li>use {@link Appendable#append(CharSequence)} in {@link #copyTo(Appendable)} and {@link
   *       #copyTo(CharSink)}. We know this is correct since strings are immutable and so the length
   *       can't change, and it is faster because many writers and appendables are optimized for
   *       appending string instances.
   * </ul>
   */

   * <p>Calling {@code setDistinctValues(type, v1, v2)} also sets the default value for {@code type}
   * that's used for {@link #testNulls}.
   *
   * <p>Only necessary for types where {@link ClassSanityTester} doesn't already know how to create
   * distinct values.
   *
   * @return this tester instance
   * @since 17.0
   */
  @CanIgnoreReturnValue
  public <T> ClassSanityTester setDistinctValues(Class<T> type, T value1, T value2) {

   *       one with {@link CharSequence#charAt(int)}.
   *   <li>use {@link Appendable#append(CharSequence)} in {@link #copyTo(Appendable)} and {@link
   *       #copyTo(CharSink)}. We know this is correct since strings are immutable and so the length
   *       can't change, and it is faster because many writers and appendables are optimized for
   *       appending string instances.
   * </ul>
   */

    assertThat(verifier.verify("\u2121.com", session)).isFalse()
    assertThat(verifier.verify("℡.com", session)).isFalse()

    // These should ideally be false, but we know that hostname is usually already checked by us
    assertThat(verifier.verify("\u212A.com", session)).isFalse()
    // Kelvin character below
    assertThat(verifier.verify("K.com", session)).isFalse()
  }

   */
  public static int frequency(Iterator<?> iterator, @Nullable Object element) {
    int count = 0;
    while (contains(iterator, element)) {
      // Since it lives in the same class, we know contains gets to the element and then stops,
      // though that isn't currently publicly documented.
      count++;
    }
    return count;
  }

  /**

      return true
    }
  }

  /**
   * HTTP/2 can have both stream timeouts (due to a problem with a single stream) and connection
   * timeouts (due to a problem with the transport). When a stream times out we don't know whether
   * the problem impacts just one stream or the entire connection.
   *
   * To differentiate the two cases we ping the server when a stream times out. If the overall

                 * *get* call in getValue but not for the *put* call here.)
                 *
                 * (Arguably we should use requireNonNull rather than uncheckedCastNullableTToT: We
                 * know that V is a non-null type because that's the only kind of value type that
                 * StandardTable supports. Thus, requireNonNull is safe as long as the cell is still

   * both use cases by using @PolyNull. (By contrast, we can't use @PolyNull for our superinterface
   * (`implements Function<@PolyNull A, @PolyNull B>`), at least as far as I know.)
   */
  public Iterable<B> convertAll(Iterable<? extends A> fromIterable) {
    checkNotNull(fromIterable, "fromIterable");
    return () ->
        new Iterator<B>() {

   * <p>Calling {@code setDistinctValues(type, v1, v2)} also sets the default value for {@code type}
   * that's used for {@link #testNulls}.
   *
   * <p>Only necessary for types where {@link ClassSanityTester} doesn't already know how to create
   * distinct values.
   *
   * @return this tester instance
   * @since 17.0
   */
  @CanIgnoreReturnValue
  public <T> ClassSanityTester setDistinctValues(Class<T> type, T value1, T value2) {

        return unsafeNull(); // See the discussion in getValue().
      }
      /*
       * The cast is safe because updateIndex found the entry for this key. (If it hadn't, then we
       * would have returned above.) Thus, we know that it and its corresponding value are in
       * position `index`.
       */
      V oldValue = uncheckedCastNullableTToT(values[index]);
      if (Objects.equals(oldValue, value)) {
        return value;
      }