def unavailable(from)
      doc = Document.new
      doc.create_element('presence',
        'from' => from.to_s,
        'id'   => Kit.uuid,
        'type' => 'unavailable')
    end
def unavailable(from)
      doc = Document.new
      doc.create_element('presence',
        'from' => from.to_s,
        'id'   => Kit.uuid,
        'type' => 'unavailable')
    end
Return an unavailable presence stanza addressed from the given JID.