def _cleanup(self):
        self._declare_cb = None
        self._delete_cb = None
        super(ExchangeClass, self)._cleanup()
list * size -> window iterable
dataset/ETHPy150Open agoragames/haigha/haigha/classes/exchange_class.py/ExchangeClass._cleanup--crossover with--dataset/ETHPy150Open ProgVal/Limnoria/src/utils/seq.py/window