一段错误的代码

from tkinter import *

class CanvasDemo:
def __init__(self):
window = Tk()
window.title("Canvas Demo")

self.canvas = Canvas(window, width=200, height=100, bg="white")
self.canvas.pack()

frame = Frame(window)
frame.pack()
btRectangle = Button(frame, text="Rectangle", command=self.displayRect)
btOval = Button(frame, text="Oval", command=self.displayOval)
btArc = Button(frame, text="Arc", command=self.displayArc)
btPolygon = Button(frame, text="Polygon", command=self.displayPolygon)
btLine = Button(frame, text="Line", command=self.displayLine)
btString = Button(frame, text="String", command=self.displayString)
btClear = Button(frame, text="Clear", command=self.clearCanvas)
btRectangle.grid(row=1, column=1)
btOval.grid(row=1, column=2)
btArc.grid(row=1, column=3)
btPolygon.grid(row=1, column=4)
btLine.grid(row=1, column=5)
btString.grid(row=1, column=6)
btClear.grid(row=1, column=7)

window.mainloop()

def displayRect(self):
self.canvas.create_rectangle(10, 10, 190, 90, tags="rect")

def displayOval(self):
self.canvas.create_oval(10, 10, 190, 90, fill="red", tags="oval")

def displayArc(self):
self.canvas.create_arc(
10, 10, 190, 90, start=0, extent=90, width=8, fill="red", tags="arc"
)

def displayPolygon(self):
self.canvas.create_polygon(10, 10, 190, 90, 30, 50, tags="polygon")

def displayLine(self):
self.canvas.create_line(10, 10, 190, 90, fill="red", tags="line")

def displayString(self):
self.canvas.create_text(
60,
40,
text="Hi, I am a string",
font="Times 10 bold underline",
tags="String",
)

def clearCanvas(self):
self.canvas.delete("rect", "oval", "arc", "polygon", "line", "string")

CanvasDemo()