Turtle bgpic（）没有显示图像并给了我这些错误消息……？

Question

我正在尝试让Turtle图形显示背景图像。

这是我的代码：

import turtle
from turtle import *
from appJar import gui
...
turtle.setup(900,700)       #windowsize
Ian = turtle.Turtle()
Ian.hideturtle()
Ian.screen.title("Arp Convertor")
Ian.screen.bgcolor("#4a4a54")           
Ian.screen.bgpic('Backwslots2.gif')
Ian.speed(0)
Ian.penup()                             #dont draw
Ian.goto(-430,250)                      #where we'll start drawing

我的图片大小合适，在当前目录中正好为900x700（与我的.py文件相同）。但是bgpic（）行给了我这些错误。

> Exception in Tkinter callback Traceback (most recent call last):  
> File
> "C:\Users\Ian\AppData\Local\Programs\Python\Python37-32\lib\tkinter\__init__.py",
> line 1705, in __call__
>     return self.func(*args)   File "D:\Midipy\appJar\appjar.py", line 3574, in <lambda>
>     return lambda *args: funcName(param)   File "midipy.py", line 21, in openthefile
>     convertthefile(btn)   File "midipy.py", line 141, in convertthefile
>     Ian.screen.bgpic('Backwslots2.gif')   File "C:\Users\Ian\AppData\Local\Programs\Python\Python37-32\lib\turtle.py",
> line 1482, in bgpic
>     self._setbgpic(self._bgpic, self._bgpics[picname])   File "C:\Users\Ian\AppData\Local\Programs\Python\Python37-32\lib\turtle.py",
> line 738, in _setbgpic
>     self.cv.itemconfig(item, image=image)