在只读模式下从组合框中删除突出显示（python）

Question

当用户选择一个选项时，我想从combobox小部件中删除高亮显示。但是select\u clear（）方法似乎不起作用：（

有什么线索吗？

from tkinter import *
from tkinter.ttk import Combobox

class hey(Frame):
    def __init__(self):
        Frame.__init__(self)

        self.comboboxVariable = StringVar()
        values = (1, 2, 3, 4, 5)

        self.comboBox = Combobox(self, textvariable = self.comboboxVariable, values = values, state = 'readonly')
        self.comboBox.pack()

        self.comboBox.bind("<<ComboboxSelected>>", self.updateData)

    def updateData(self, event =None):

        self.comboBox.select_clear()


myClass = hey()
myClass.pack()
root = myClass.master
root.mainloop()