device.xml

<iq from="juliet@capulet.lit" type="set" id="announce2">
  <pubsub xmlns="http://jabber.org/protocol/pubsub">
    <publish node="eu.siacs.conversations.axolotl.bundles:31415">
      <item id="current">
        <bundle xmlns="eu.siacs.conversations.axolotl">
          <identityKey>QkFTRTY0IEVOQ09ERUQ=</identityKey>
          <prekeys>
            <preKeyPublic preKeyId="1">QkFTRTY0IEVOQ09ERUQ=</preKeyPublic>
            <preKeyPublic preKeyId="2">QkFTRTY0IEVOQ09ERUQ=</preKeyPublic>
            <preKeyPublic preKeyId="3">QkFTRTY0IEVOQ09ERUQ=</preKeyPublic>
          </prekeys>
          <signedPreKeySignature>QkFTRTY0IEVOQ09ERUQ=</signedPreKeySignature>
          <signedPreKeyPublic signedPreKeyId="1">QkFTRTY0IEVOQ09ERUQ=</signedPreKeyPublic>
        </bundle>
      </item>
    </publish>
  </pubsub>
</iq>