About "The Warriors"

I passed "The Warriors" mission on my PC (python 3.7.4), but in "check" mode on checkio, an error caused.

From: https://py.checkio.org/mission/the-warriors/solve/

Error description:

return iterencode(o, 0), File "/usr/local/lib/python3.8/json/encoder.py", line 179, in default, raise TypeError(f'Object of type {o.class.name} ',TypeError: Object of type method is not JSON serializable,,During handling of the above exception, another exception occurred:,,Traceback (most recent call last):, File "/home/site/checkio/runners/py32.py", line 486, in , rundata = echosendrecvjson(globals()'do' + rundata['do']), File "/home/site/checkio/runners/py32.py", line 255, in echosendrecvjson, error = u'TypeError: {0} is wrong data type'.format(cgi.escape(str(type(result)))),AttributeError: module 'cgi' has no attribute 'escape',

My solution:

class Warrior:
    health = 50
    attack = 5


    def is_alive(self):
        if self.health > 0:
            return True
        else:
            return False


class Knight(Warrior):
    attack = Warrior.attack + 2


def fight(unit_1, unit_2):
    while unit_1.health > 0 and unit_2.health > 0:
        unit_2.health = unit_2.health - unit_1.attack
        if unit_2.health > 0:
            unit_1.health = unit_1.health - unit_2.attack
        else:
            return True
    else:
        return False