the core type of <code>T</code> is called <code>bytestring</code>.
</p>

<p>
Examples of interfaces with <code>bytestring</code> core types:
</p>

<pre>
interface{ int }                          // int (same as ordinary core type)
interface{ []byte | string }              // bytestring
interface{ ~[]byte | myString }           // bytestring
</pre>

<p>

    that `tag()` now returns null if the request has no tag. Previously this would return the
    request itself.
 *  New: `Headers.Builder.addAll(Headers)`.
 *  New: `ResponseBody.create(MediaType, ByteString)`.
 *  New: Embed R8/ProGuard rules in the jar. These will be applied automatically by R8.
 *  Fix: Release the connection if `Authenticator` throws an exception.

  // 2. the order is deterministic and easy to understand, for debugging purpose.
  @SuppressWarnings("ComparableType")
  private static final class ByToString implements Comparable<Object>, Serializable {
    private static final ByToString INSTANCE = new ByToString();

    @Override
    public int compareTo(Object o) {
      return toString().compareTo(o.toString());
    }

    @Override

  // 2. the order is deterministic and easy to understand, for debugging purpose.
  @SuppressWarnings("ComparableType")
  private static final class ByToString implements Comparable<Object>, Serializable {
    private static final ByToString INSTANCE = new ByToString();

    @Override
    public int compareTo(Object o) {
      return toString().compareTo(o.toString());
    }

    @Override