Problem with Warlord mission

In this mission: https://py.checkio.org/ru/mission/the-warlords/

I get this error: https://prnt.sc/1sowfaw

How to resolve it? Thank you for your time.

    class Warrior:
        def __init__(self):
            self.health = 50
            self.max_health = 50
            self.attack = 5

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

        def equip_weapon(self, weapon):
            self.health += weapon.health
            self.max_health += weapon.health
            self.attack += weapon.attack

            if hasattr(self, 'vampirism') and hasattr(weapon, 'vampirism'):
                self.vampirism += weapon.vampirism

            if hasattr(self, 'defense') and hasattr(weapon, 'vampirism'):
                self.defense += weapon.defense

            if hasattr(self, 'heal_power') and hasattr(weapon, 'vampirism'):
                self.heal_power += weapon.heal_power


    class Lancer(Warrior):
        # первому, стоящему перед ним сопернику, он наносит урон в размере 100% своей атаки
        # (с учетом защиты соперника, если она есть), а сопернику, который стоит позади - 50% от
        # нанесенного урона (защита соперника уменьшает наносимый копейщиком урон и,
        # соответственно, получаемый вторым юнитом урон).
        def __init__(self):
            super().__init__()
            self.attack = 6


    class Vampire(Warrior):
        def __init__(self):
            super().__init__()
            self.max_health = 40
            self.health = 40
            self.attack = 4
            self.vampirism = 50


    class Defender(Warrior):
        def __init__(self):
            super().__init__()
            self.max_health = 60
            self.health = 60
            self.attack = 3
            self.defense = 2


    class Knight(Warrior):
        def __init__(self):
            super().__init__()
            self.attack = 7


    class Healer(Warrior):
        # Каждый раз, когда союзный солдат бьет врага, Healer, стоящий позади союзника лечит его на +2
        # единицы здоровья. При этом исцеление не может поднять здоровье выше максимального уровня.
        def __init__(self):
            super().__init__()
            self.max_health = 60
            self.health = 60
            self.attack = 0
            self.heal_pwr = 2

        def heal(self, unit):
            unit.health = min(unit.max_health, unit.health + self.heal_pwr)


    class Warlord(Warrior):
        def __init__(self):
            super().__init__()
            self.max_health = 100
            self.health = 100
            self.attack = 4
            self.defense = 2

    ########################################################################


    class Weapon:
        def __init__(self, health, attack, defense, vampirism, heal_power):
            self.health = health
            self.attack = attack
            self.defense = defense
            self.vampirism = vampirism
            self.heal_power = heal_power

    class Sword(Weapon):
        def __init__(self):
            self.health = 5
            self.attack = 2

    class Shield(Weapon):
        def __init__(self):
            self.health = 20
            self.attack = -1
            self.defense = 2

    class GreatAxe(Weapon):
        def __init__(self):
            self.health = -15
            self.attack = 5
            self.defense = -2
            self.vampirism = 10

    class Katana(Weapon):
        def __init__(self):
            self.health = -20
            self.attack = 6
            self.defense = -5
            self.vampirism = 10

    class MagicWand(Weapon):
        def __init__(self):
            self.health = 30
            self.attack = 3
            self.heal_power = 3


    ########################################################################

    def lancer_attack(lancer, enemy):
        damage = 0
        if type(enemy) == Defender and lancer.attack > enemy.defense:
            damage = lancer.attack/2 - enemy.defense
        else:
            damage = lancer.attack/2
        enemy.health -= damage
        return enemy

    def fight(unit_1, unit_2, i=0, army1=False, army2=False, healer_1=False, healer_2=False):
        damage = 0
        while unit_1.is_alive and unit_2.is_alive:
            if army1 and army2 and type(unit_1) == Lancer and len(army2.units)-1>i:
                army2.units[i+1] = lancer_attack(army1.units[i], army2.units[i+1])

            if type(unit_2) == Defender:
                if unit_1.attack > unit_2.defense:
                    damage = unit_1.attack - unit_2.defense
                    unit_2.health -= damage
            else:
                damage = unit_1.attack
                unit_2.health -= damage

            if type(unit_1) == Vampire and damage != 0:
                unit_1.health += int(damage * unit_1.vampirism / 100)
                if unit_1.health > unit_1.max_health:
                    unit_1.health = unit_1.max_health

            if unit_1.is_alive and healer_1:
                healer_1.heal(unit_1)

            # Если второй воин (которого ударили) еще живой
            if unit_2.is_alive:
                if army1 and army2 and type(unit_2) == Lancer and len(army1.units)-1>i:
                    army1.units[i+1] = lancer_attack(army2.units[i], army1.units[i+1])

                if type(unit_1) == Defender:
                    if unit_2.attack > unit_1.defense:
                        damage = unit_2.attack - unit_1.defense
                        unit_1.health -= damage

                else:
                    damage = unit_2.attack
                    unit_1.health -= damage

                if type(unit_2) == Vampire and damage != 0:
                    unit_2.health += int(damage * unit_2.vampirism / 100)
                    if unit_1.health > unit_1.max_health:
                        unit_1.health = unit_1.max_health

                if unit_2.is_alive and healer_2:
                    healer_2.heal(unit_2)

        if unit_1.is_alive and not unit_2.is_alive:
            return True
        return False


    class Army:
        def __init__(self):
            self.units = []

        def add_units(self, units, count):
            for x in range(count):
                self.units.append(units())

        def move_units(self):
            warlord = [x for x in self.units if type(x)==Warlord]
            if warlord:
                lancers = [x for x in self.units if type(x)==Lancer]
                healers = [x for x in self.units if type(x)==Healer]
                soldiers = [x for x in self.units if not isinstance(x, (Lancer, Healer, Warlord))]
                warlord = [x for x in self.units if type(x)==Warlord]
                self.units = []
                if lancers:
                    self.units.append(lancers[0])
                else:
                    self.units.append(soldiers[0])
                if healers:
                    self.units.extend(healers)
                if len(lancers)>1:
                    self.units.extend(lancers[1:])
                if lancers:
                    self.units.extend(soldiers)
                else:
                    self.units.extend(soldiers[1:])
                self.units.extend(warlord)


    def delete_zero(grp):
        """Удаляем ноли из списка с группами ламп"""
        import itertools as it
        neo = list(it.filterfalse(lambda x: x == 0, grp))
        return neo

    class Battle:
        def fight(self, army1, army2):
            if isinstance(army1, Army) and isinstance(army2, Army):
                army1.move_units()
                army2.move_units()
                while len(army1.units) and len(army2.units):
                    healer_1, healer_2 = False, False
                    if len(army1.units)>1:
                        healer_1 = army1.units[1] if type(army1.units[1]) == Healer else False
                    if len(army2.units)>1:
                        healer_2 = army2.units[1] if type(army2.units[1]) == Healer else False

                    first_wins = fight(army1.units[0], army2.units[0], 0, army1, army2, healer_1, healer_2)
                    if first_wins:
                        del army2.units[0]
                        army2.move_units()
                    else:
                        del army1.units[0]
                        army1.move_units()

                if army1.units:
                    return True
                return False
            else:
                print('Not correct input!')

        def straight_fight(self, army1, army2):
            while army1.units and army2.units:
                i = 0
                for x, y in zip(army1.units, army2.units):
                    first_wins = fight(x, y)
                    if first_wins:
                        army2.units[i] = 0
                    else:
                        army1.units[i] = 0
                    i += 1

                army1.units = delete_zero(army1.units)
                army2.units = delete_zero(army2.units)

            if army1.units:
                return True
            return False