Walk through nested dic and return with parent

gistfile1.py

dic = {
    "root_grp": {
        "a":{
            "a1":{
                "aa1":{},
                "aa2":{}
            },
            "a2":{}
        } ,

        "b":{
            "b1":{},
            "b2":{

                "c":{
                    "c1":{} ,
                    "c2":{}
                },
                "d":{
                    "d1":{},
                    "d2":{}
                }
            }
        }
    }
}

class walk():
    
    I = 0
    PARENT_LIST = []
    PARENT = None

    @classmethod
    def run(cls, dic, parent=None):
        for key , item in dic.items():
            print(walk.PARENT, key)
            if len(item.keys()) > 0:
                parent = key

                walk.PARENT_LIST.append(parent)
                walk.PARENT = parent
                cls.run(item, parent=parent)

            else:
                try:
                    walk.PARENT = walk.PARENT_LIST[-1]
                    del walk.PARENT_LIST[-1]
                except:
                    pass


walk.run(dic)