string containing both a certificate and PKCS #8-encoded private key.

    ```kotlin
    val heldCertificate = HeldCertificate.decode("""
        |-----BEGIN CERTIFICATE-----
        |MIIBYTCCAQegAwIBAgIBKjAKBggqhkjOPQQDAjApMRQwEgYDVQQLEwtlbmdpbmVl
        |cmluZzERMA8GA1UEAxMIY2FzaC5hcHAwHhcNNzAwMTAxMDAwMDA1WhcNNzAwMTAx

    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
  }

  /**
   * Evaluates whether the argument is a 6to4 address.
   *
   * <p>6to4 addresses begin with the {@code "2002::/16"} prefix. The next 32 bits are the IPv4
   * address of the host to which IPv6-in-IPv4 tunneled packets should be routed.
   *
   * <p>For more on 6to4 addresses see section 2 of <a target="_parent"

 */
abstract class EventListener {
  /**
   * Invoked as soon as a call is enqueued or executed by a client. In case of thread or stream
   * limits, this call may be executed well before processing the request is able to begin.
   *
   * This will be invoked only once for a single [Call]. Retries of different routes or redirects
   * will be handled within the boundaries of a single [callStart] and [callEnd]/[callFailed] pair.
   */

    // unless taskFuture is cancelled, in which case it falls back to oldFuture. This ensures that
    // if the future we return is cancelled, we don't begin execution of the next task until after
    // oldFuture completes.
    Runnable listener =
        () -> {
          if (taskFuture.isDone()) {

      return false;
    }

    /*
     * Note that we allow (in contravention of a strict interpretation of the relevant RFCs) domain
     * parts other than the last may begin with a digit (for example, "3com.com"). It's important to
     * disallow an initial digit in the last part; it's the only thing that stops an IPv4 numeric
     * address like 127.0.0.1 from looking like a valid domain name.

			expectedAuthField: signValues{},
			expectedErrCode:   ErrAuthHeaderEmpty,
		},
		// Test case - 2.
		// Test case with no sign v4 Algorithm prefix.
		// A valid authorization string should begin(prefix)
		{
			inputV4AuthStr:    "no-singv4AlgorithmPrefix",
			expectedAuthField: signValues{},
			expectedErrCode:   ErrSignatureVersionNotSupported,
		},
		// Test case - 3.

    return getInet4Address(Arrays.copyOfRange(ip.getAddress(), 12, 16));
  }

  /**
   * Evaluates whether the argument is a 6to4 address.
   *
   * <p>6to4 addresses begin with the {@code "2002::/16"} prefix. The next 32 bits are the IPv4
   * address of the host to which IPv6-in-IPv4 tunneled packets should be routed.
   *
   * <p>For more on 6to4 addresses see section 2 of <a target="_parent"

    }
  }

  /**
   * Removes a number of occurrences of the specified element from this multiset. If the multiset
   * contains fewer than this number of occurrences to begin with, all occurrences will be removed.
   *
   * @param element the element whose occurrences should be removed
   * @param occurrences the number of occurrences of the element to remove

           * go out of date (for a collection like CopyOnWriteArrayList, which may have been safely
           * modified concurrently), or it might have been only an estimate to begin with (for a
           * collection like ConcurrentHashMap, which sums up several counters that may not be in
           * sync with one another). We accommodate that by resizing as necessary.
           */

  @Override
  boolean add(@ParametricNullness E element);

  /**
   * Removes a number of occurrences of the specified element from this multiset. If the multiset
   * contains fewer than this number of occurrences to begin with, all occurrences will be removed.
   * Note that if {@code occurrences == 1}, this is functionally equivalent to the call {@code
   * remove(element)}.
   *