ValueError: <__main__.Enemy object at 0x07BFE2F8> is not in list

I trying to make spaceship game from using pygame. Just simple game what warship shoot bullet and collide enemies. But when I play my game, after 6 or 7 collisions I get below error.

import pygame
import random
import time

WIDTH, HEIGHT = (750, 600)

WIN = pygame.display.set_mode((WIDTH, HEIGHT))
pygame.display.set_caption("Space İnvader Game")
BG_IMAGE = pygame.transform.scale(pygame.image.load("yeni_resim.jpg"), (WIDTH, HEIGHT))
CAPTION_IMAGE = pygame.image.load("spaceship.png")
ENEMY_IMAGE = pygame.image.load("enemy.png")
BULLET_IMAGE = pygame.image.load("bullet.png")
PLAYER_IMAGE = pygame.image.load("warship.png")

creating bullet class

class Bullet:
    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.img = BULLET_IMAGE
        self.mask = pygame.mask.from_surface(self.img)
        self.vel = 8
        self.hitbox = (self.x, self.y, 32,32)

    def draw(self, window):
        window.blit(self.img, (self.x, self.y))
        self.hitbox = (self.x, self.y, 32, 32)
        pygame.draw.rect(window,(0,0,255),self.hitbox,2)

    def get_width(self):
        return self.img.get_width()

    def get_height(self):
        return self.img.get_height()

    def collide(self, obj1, obj2):
        self.offset_x = obj2.x - obj1.x
        self.offset_y = obj2.y - obj1.y
        return obj1.mask.overlap(obj2.mask , (self.offset_x, self.offset_y)) != None

class Ship:
    def __init__(self, x, y,width,height):
        self.x = x
        self.y = y
        self.width = width
        self.height = height
        self.ship_img = None


    def draw(self, window):
        window.blit(self.ship_img, (self.x, self.y))


    def get_width(self):
        return self.ship_img.get_width()

    def get_height(self):
        return self.ship_img.get_height()


class Player(Ship):

    def __init__(self, x, y,width,height):
        super().__init__(x, y,width,height)
        self.ship_img = PLAYER_IMAGE
        self.mask = pygame.mask.from_surface(self.ship_img)
        self.hitbox = (self.x, self.y, 64, 64)

    def draw(self, window):
        super().draw(window)
        self.hitbox = (self.x , self.y , 64, 64)
        pygame.draw.rect(window, (0, 0, 255), self.hitbox, 2)

creating enemy class and defining collide def

class Enemy():

    def __init__(self, x, y):
        self.x = x
        self.y = y
        self.ship_img = ENEMY_IMAGE
        self.mask = pygame.mask.from_surface(self.ship_img)
        self.enemy_vel = 4
        self.hitbox = (self.x, self.y, 64, 64)

    def draw(self, window):
        self.hitbox = (self.x, self.y, 64, 64)
        window.blit(self.ship_img,(self.x, self.y))
        pygame.draw.rect(window, (255,0,0),self.hitbox,2)

    def move(self,x,y):
        self.x = x
        self.y = y
        self.x += self.enemy_vel
        if self.x >= 686 or self.x <= 0:
            self.enemy_vel *= -1
            self.y += 5

    def get_width(self):
        return self.ship_img.get_width()
    def get_height(self):
        return self.ship_img.get_height()

    def hit(self):
        print("Hit")

    def collide(self,obj1, obj2):
        self.offset_x = obj2.x - obj1.x
        self.offset_y = obj2.y - obj1.y
        return obj1.mask.overlap(obj2.mask , (self.offset_x, self.offset_y)) != None




def main():
    run = True
    FPS = 60
    clock = pygame.time.Clock()
    bullets = []
    enemies = []
    player = Player(350, 500,64,64)
    player_vel = 8
    enemy_vel = 3




    def redraw_window():
        WIN.blit(BG_IMAGE,(0,0))
        player.draw(WIN)
        for bullet in bullets:
            bullet.draw(WIN)
        for enemy in enemies:
            enemy.draw(WIN)
        pygame.display.update()

calling collide definition in for enemy loop

    while run:
        clock.tick(FPS)
        redraw_window()


        if len(enemies) < 8:
            enemies.append(Enemy(random.randint(0, 600), random.randint(0,200)))

        for enemy in enemies:
            enemy.move(enemy.x, enemy.y)
            for bullet in bullets:
                if bullet.collide(enemy,bullet):
                    enemies.pop(enemies.index(enemy))
                    bullets.pop(bullets.index(bullet))




        for bullet in bullets:
            if bullet.y < 600 and bullet.y > 0:
                bullet.y -= bullet.vel
            else:
                bullets.pop(bullets.index(bullet))


        keys = pygame.key.get_pressed()
        if keys[pygame.K_RIGHT] and player.x + player_vel + player.get_width() < WIDTH:
            player.x += player_vel
        if keys[pygame.K_LEFT] and player.x - player_vel > 0:
            player.x -= player_vel
        if keys[pygame.K_SPACE]:
            if len(bullets) < 10:
                bullets.append(Bullet(round(player.x + 17),round(player.y)))



        for event in pygame.event.get():
            if event.type == pygame.QUIT:
                run = False


main()

Then take this error after 6 or 7 time collision

C:Users191119AppDataLocalProgramsPythonPython38-32python.exe "C:/Users/191119/PycharmProjects/Pygame Projects2/AIGAMES.py"
pygame 1.9.6
Hello from the pygame community. https://www.pygame.org/contribute.html
Traceback (most recent call last):
  File "C:/Users/191119/PycharmProjects/Pygame Projects2/AIGAMES.py", line 180, in <module>
    main()
  File "C:/Users/191119/PycharmProjects/Pygame Projects2/AIGAMES.py", line 151, in main
    enemies.pop(enemies.index(enemy))
ValueError: <__main__.Enemy object at 0x07527868> is not in list