"42.42.42.ab",
            "3ffe::1.net",
            "3ffe::1::1",
            "1::2::3::4:5",
            "::7:6:5:4:3:2:", // should end with ":0"
            ":6:5:4:3:2:1::", // should begin with "0:"
            "2001::db:::1",
            "FEDC:9878",
            "+1.+2.+3.4",
            "1.2.3.4e0",
            "6:5:4:3:2:1:0", // too few parts
            "::7:6:5:4:3:2:1:0", // too many parts

    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"

   *
   * <p>If a task is {@linkplain Thread#interrupt interrupted} while a task is running:
   *
   * <ol>
   *   <li>execution will not stop until the task queue is empty.
   *   <li>tasks will begin execution with the thread marked as not interrupted - any interruption
   *       applies only to the task that was running at the point of interruption.

    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"

   *
   * <p>If a task is {@linkplain Thread#interrupt interrupted} while a task is running:
   *
   * <ol>
   *   <li>execution will not stop until the task queue is empty.
   *   <li>tasks will begin execution with the thread marked as not interrupted - any interruption
   *       applies only to the task that was running at the point of interruption.

 * <h4>Automatically closing</h4>
 *
 * You can extract a {@link Future} that represents the result of the last step in the pipeline by
 * calling {@link #finishToFuture()}. All objects the pipeline has captured for closing will begin
 * to be closed asynchronously <b>after</b> the returned {@code Future} is done: the future
 * completes before closing starts, rather than once it has finished.
 *
 * <pre>{@code
 * FluentFuture<UserName> userName =

 * <h4>Automatically closing</h4>
 *
 * You can extract a {@link Future} that represents the result of the last step in the pipeline by
 * calling {@link #finishToFuture()}. All objects the pipeline has captured for closing will begin
 * to be closed asynchronously <b>after</b> the returned {@code Future} is done: the future
 * completes before closing starts, rather than once it has finished.
 *
 * <pre>{@code
 * FluentFuture<UserName> userName =