code: def add_cvi_loopback(self, address, ospf_area=None, **kw):
          
          lb = self.create(address, ospf_area, **kw)
         
          if self.typeof in self._engine.data:
              self._engine.data[self.typeof].append(lb.data)
          else:
              self._engine.data[self.typeof] = [lb.data]
          
          self._engine.update()
docs: Add a loopback interface as a cluster virtual loopback. This enables
          the loopback to 'float' between cluster members. Changes are committed
          immediately.
          
          :param str address: ip address for loopback
          :param int rank: rank of this entry
          :param str,Element ospf_area: optional ospf_area to add to loopback
          :raises UpdateElementFailed: failure to save loopback address
          :return: None