def expand(self, problem):
        "List the nodes reachable in one step from this node."
        return [self.child_node(problem, action)
                for action in problem.actions(self.state)]
def expand(self, problem):
        "List the nodes reachable in one step from this node."
        return [self.child_node(problem, action)
                for action in problem.actions(self.state)]
def expand ( self , problem ) : return [ self . child_node ( problem , action ) for action in problem . actions ( self . state ) ]
List the nodes reachable in one step from this node.
List the nodes reachable in one step from this node .