自变量被视为一个参数

Question

我已经来过一段时间了，但是我没有看到这个问题。当我在DBSyncRoot类中调用addSyncPoints函数时，它告诉我它需要2个参数，但我只给出了一个。有人可以告诉我为什么吗？自变量应该是类声明本身，不是吗？

from tkinter import *
from tkinter import ttk

class DBSyncRoot(Tk):
    def __init__(self):
        defaultBackColor = "Black"
        defaultForeColor = "White"
        super(DBSyncRoot, self).__init__() # Not sure why this is required.   Found it at https://www.youtube.com/watch?v=VGIK3P9gNkM
        # Setting up the main form.
        self.title("DBSync")
        self.geometry("500x300")
        self.minsize(500,300)
        self.maxsize(500,300)
        self.wm_iconbitmap("sync.ico") # https://icons8.com/icon/set/sync/all and converted with https://icoconvert.com
        self.configure(background="black")

        # The dropdown Menu

        self.menuBar = Menu(self)
        self.fileMenu = Menu(self.menuBar, tearoff=0)
        self.helpMenu = Menu(self.menuBar, tearoff=0)
        self.config(menu=self.menuBar)

        self.menuBar.add_cascade(label="File", menu=self.fileMenu) # Add the top "File" menu.
        self.fileMenu.add_command(label="Quit", command=self.destroy)

        self.menuBar.add_cascade(label="Help", menu=self.helpMenu) # Add the top "Help" menu.
        self.helpMenu.add_command(label="About")

        # The combobox
        self.lblSyncPoint = Label(text = "Sync Points", background=defaultBackColor, foreground = defaultForeColor)
        self.combo = ttk.Combobox(self, width = 25, background=defaultBackColor, foreground=defaultForeColor)

        self.lblSyncPoint.place(x=0, y=0)
        self.combo.place(x = 30, y = 25)

    def addSyncPoints(self, syncPoint):
        self.combo["values"] += syncPoint


if __name__=="__main__":
    DBSync = DBSyncRoot()
    DBSyncRoot.addSyncPoints("Apple")
    DBSync.mainloop()