code: def nodes(self):
          
          resource = sub_collection(
              self.get_relation( 
                  'nodes'), 
              Node) 
          resource._load_from_engine(self, 'nodes') 
          return resource
docs: Return a list of child nodes of this engine. This can be
          used to iterate to obtain access to node level operations
          ::
          
              >>> print(list(engine.nodes))
              [Node(name=myfirewall node 1)]
              >>> engine.nodes.get(0)
              Node(name=myfirewall node 1)
              
          
          :return: nodes for this engine
          :rtype: SubElementCollection(Node)