What line of code do I use to erase all the Sprites on my screen?

I am programming an Art app and I've came to a block which is How to erase all of the sprites on the screen. now I have searched on videos which directed me to this function: kill(). I have tried kill() in my code and has led me to a crash either to my window or to sensing whether I clicked a button on the screen.
this is my line of code

   import pygame as pg
   all_sprites = pg.sprite.Group()
   pg.init()
   win = pg.display.set_mode((600, 600))
   icon = pg.image.load('paint icon')
   pg.display.set_icon(icon)
   black = (0,0,0)
   grey = (128,128,128)
   white = (255,255,255)
   hpink = (255, 0, 64)
   lpink = (255, 192, 255)
   pink = (255, 128, 255)
   fuchsia = (255, 0, 128)
   red = (255,0,0)
   orange = (255,128,0)
   brown = (192,100,0)
   lbrown = (200,108,0)
   yellow = (255,192,0)
   green = (0,255,0)
   lblue = (0,128,255)
   blue = (0,0,255)
   dblue = (0,0,128)
   purple = (128,0,128)
   click = 0
   win.fill(white)
   w = 10
   h = 10

   class Ink(pg.sprite.Sprite):
       def __init__(self):
           pg.sprite.Sprite.__init__(self)
           super(Ink,self).__init__()
           self.image = pg.Surface([w,h])
           self.rect = self.image.get_rect()
           self.image.fill(black)

    class Drop(pg.sprite.Sprite):
        def __init__(self):
            super(Drop,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([180,300])
            self.rect = self.image.get_rect()
            self.image.fill(brown)
        def update(self):
            if exit.rect.collidepoint(pos):
                if pg.mouse.get_pressed()[0]:


    class Box(pg.sprite.Sprite):
        def __init__(self):
            super(Box,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([50,30])
            self.rect = self.image.get_rect()
            self.image.fill(green)


    class Exit(pg.sprite.Sprite):
        def __init__(self):
            super(Exit,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([40,20])
            self.rect = self.image.get_rect()
            self.image.fill(lbrown)



    class Red(pg.sprite.Sprite):
        def __init__(self):
            super(Red,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([20,20])
            self.rect = self.image.get_rect()
            self.image.fill(red)

    class Orange(pg.sprite.Sprite):
        def __init__(self):
            super(Orange,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([20,20])
            self.rect = self.image.get_rect()
            self.image.fill(orange)

    class Yellow(pg.sprite.Sprite):
        def __init__(self):
            super(Yellow,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([20,20])
            self.rect = self.image.get_rect()
            self.image.fill(yellow)

    class Green(pg.sprite.Sprite):
        def __init__(self):
            super(Green,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([20,20])
            self.rect = self.image.get_rect()
            self.image.fill(green)
    class Blue(pg.sprite.Sprite):
        def __init__(self):
            super(Blue,self).__init__()
            pg.sprite.Sprite.__init__(self)
            self.image = pg.Surface([20,20])
            self.rect = self.image.get_rect()
            self.image.fill(blue)


    ink = Ink()
    ink.rect.x = 100
    ink.rect.y = 300
    drop = Drop()
    drop.rect.x = 390
    drop.rect.y = 133
    box = Box()
    box.rect.x = 420
    box.rect.y = 528
    exit = Exit()
    exit.rect.x = 530
    exit.rect.y = 138

    redc = Red()
    redc.rect.x = 400
    redc.rect.y = 600//3.5
    orangec = Orange()
    orangec.rect.x = 430
    orangec.rect.y = 600//3.5
    yellowc = Yellow()
    yellowc.rect.x = 460
    yellowc.rect.y = 600//3.5
    greenc = Green()
    greenc.rect.x = 490
    greenc.rect.y = 600//3.5
    bluec = Blue()
    bluec.rect.x = 520
    bluec.rect.y = 600//3.5
    exitc = Exit()

    def redraw():
        pg.display.update()
        all_sprites.draw(win)

    all_sprites.add(drop, box, exit)
    all_sprites.add(redc, orangec, yellowc, greenc, bluec)

    run = True

    while run:
        print(click)
        pos = pg.mouse.get_pos() ---> pos = mouse position
        print(pos) 
        for event in pg.event.get():
            key = event.type
            if key == pg.QUIT:
                run = False

        if redc.rect.collidepoint(pos):
            if pg.mouse.get_pressed()[0]:
                Ink.image.fill(red)

        if orangec.rect.collidepoint(pos):
            if pg.mouse.get_pressed()[0]:
               Ink.image.fill(orange)

        if yellowc.rect.collidepoint(pos):
            if pg.mouse.get_pressed()[0]:
                Ink.image.fill(yellow)

        if greenc.rect.collidepoint(pos):
            if pg.mouse.get_pressed()[0]:
                Ink.image.fill(green)

        if bluec.rect.collidepoint(pos):
            if pg.mouse.get_pressed()[0]:
                Ink.image.fill(blue)

        if box.rect.collidepoint(pos) and click == 0:
            if pg.mouse.get_pressed()[0]:
                all_sprites.add(ink)
                click = 1

        if box.rect.collidepoint(pos) and click == 1:
            if pg.mouse.get_pressed()[0]:
                all_sprites.remove(ink)
                click = 0

        if exit.rect.collidepoint(pos):
            exit.image.fill(red)

        else:
            exit.image.fill(lbrown)

        redraw() 
    pg.quit()

What is wrong with my code?