def unsubscribe(&blk)
      pres = connection.presence_stanza('to'=>jid.bare, 'type' => 'unsubscribe')
      connection.send_stanza pres, &blk
    end
def unsubscribe(&blk)
      pres = connection.presence_stanza('to'=>jid.bare, 'type' => 'unsubscribe')
      connection.send_stanza pres, &blk
    end
unsubscribes from from the bare entity