def _cooperation_probability(self):
        diff = (self._end_coop_prob - self._start_coop_prob)
        slope = diff / float(self._rounds_of_decay)
        rounds = len(self.history)
        return max(self._start_coop_prob + slope * rounds,
                   self._end_coop_prob)
Utility method for instantiating a DiskFile object supporting a given
dataset/ETHPy150Open Axelrod-Python/Axelrod/axelrod/strategies/axelrod_first.py/Feld._cooperation_probability--crossover with--dataset/ETHPy150Open openstack/swift/swift/obj/mem_server.py/ObjectController.get_diskfile