/** Returns the element with the specified index. This method is called by {@link #next()}. */
  @ParametricNullness
  protected abstract E get(int index);

  /**
   * Constructs an iterator across a sequence of the given size whose initial position is 0. That
   * is, the first call to {@link #next()} will return the first element (or throw {@link
   * NoSuchElementException} if {@code size} is zero).
   *

   *
   * @throws UnsupportedOperationException if this {@link EndpointPair} is not ordered
   */
  public abstract N source();

  /**
   * If this {@link EndpointPair} {@link #isOrdered()}, returns the node which is the target.
   *
   * @throws UnsupportedOperationException if this {@link EndpointPair} is not ordered
   */
  public abstract N target();

   */
  protected abstract char @Nullable [] escape(char c);

  /**
   * Returns the escaped form of a given literal string, starting at the given index. This method is
   * called by the {@link #escape(String)} method when it discovers that escaping is required. It is
   * protected to allow subclasses to override the fastpath escaping function to inline their
   * escaping test. See {@link CharEscaperBuilder} for an example usage.
   *

     *
     * @param message the detail message (which is saved for later retrieval
     *                by the {@link #getMessage()} method).
     * @param cause   the cause (which is saved for later retrieval by the
     *                {@link #getCause()} method). A {@code null} value is
     *                permitted, and indicates that the cause is nonexistent or unknown.
     */

 *  **RouteDatabase is no longer public API.** OkHttp continues to track which
    routes have failed but this is no exposed in the API.

 *  **ResponseSource is gone.** This enum exposed whether a response came from
    the cache, network, or both. OkHttp 2 offers more detail with raw access to
    the cache and network responses in the new `Response` class.

 * this class separates _allocations_ from _streams_. An allocation is created by a call, used for
 * one or more streams, and then released. An allocated connection won't be stolen by other calls
 * while a redirect or authorization challenge is being handled.
 *
 * When the maximum concurrent streams limit is reduced, some allocations will be rescinded.
 * Attempting to create new streams on these allocations will fail.

   *   <li>It is <i>distributable across equivalence</i>: for any references {@code x} and {@code
   *       y}, if {@code equivalent(x, y)}, then {@code hash(x) == hash(y)}. It is <i>not</i>
   *       necessary that the hash be distributable across <i>inequivalence</i>. If {@code
   *       equivalence(x, y)} is false, {@code hash(x) == hash(y)} may still be true.

	// in Using IAM.
	//
	// Arn is a required field
	Arn string

	// A unique identifier that contains the role ID and the role session name of
	// the role that is being assumed. The role ID is generated by AWS when the
	// role is created.
	//
	// AssumedRoleId is a required field
	AssumedRoleID string `xml:"AssumeRoleId"`
	// contains filtered or unexported fields
}

   *
   * (The index actually stored is the index of the key in alternatingKeysAndValues, which is
   * double the index of the entry in entrySet.asList.)
   *
   * The basic data structure is described in https://en.wikipedia.org/wiki/Open_addressing.
   * The pointer to a key is stored in hashTable[Hashing.smear(key.hashCode()) % table.length],
   * save that if that location is already full, we try the next index, and the next, until we

   * and response body streams; otherwise resources may be leaked.
   *
   * This method is safe to be called concurrently, but provides limited guarantees. If a transport
   * layer connection has been established (such as a HTTP/2 stream) that is terminated. Otherwise
   * if a socket connection is being established, that is terminated.
   */
  override fun cancel() {
    if (canceled) return // Already canceled.