code: def loopback_interface(self):
          
          for lb in self.data.get('loopback_node_dedicated_interface', []):
              yield LoopbackInterface(lb, self._engine)
docs: Loopback interfaces for this node. This will return
          empty if the engine is not a layer 3 firewall type::
          
              >>> engine = Engine('dingo')
              >>> for node in engine.nodes:
              ...   for loopback in node.loopback_interface:
              ...     loopback
              ... 
              LoopbackInterface(address=172.20.1.1, nodeid=1, rank=1)
              LoopbackInterface(address=172.31.1.1, nodeid=1, rank=2)
              LoopbackInterface(address=2.2.2.2, nodeid=1, rank=3)
          
          :rtype: list(LoopbackInterface)