dict class override: how access parent values?

[deanhystad]

class CSJSON(dict):
    def __setitem__(self, key : str, value : all):
       return super().__setitem__(key+'zzz', value)

    def __getitem__(self, key : str):
       return super().__getitem__(key+'zzz')

x = CSJSON()
x['Hi'] = "Hola"
x['Bye'] = 'Adios'
print(*x.keys(), x['Hi'])

Output:
Hizzz Byezzz Hola