title: Problem adding a kwarg to tk.Button subclass
body: <p>I would like to add a kwarg to a tk.Button subclass. The idea is that I would like to be able to add a number to each button of this subclass, and be able to call that number later on.</p>
  
  <pre><code>import tkinter as tk
  
  class Test(tk.Tk):
  
      def __init__(self, tasks=None):
          super().__init__()
  
  
          self.title("Test")
          self.geometry("400x600")
  
          self.container = tk.Frame(self)
          self.container.pack()
  
          self.button1 = My_buttons(self.container, text="Button 1", number=1).grid(row=0, column=0)
  
          print(self.button1.index) #here is where I would like to be able to print 1
  
  class My_buttons(tk.Button):
  
      def __init__(self, parent, *args, **kwargs):
  
          super(My_buttons, self).__init__(parent, *args, **kwargs)
          self.number = kwargs.pop("number")
  
  
  if __name__ == "__main__":
      test = Test()
      test.mainloop()
  </code></pre>
  
  <p>The above just tells me that I have a "_tkinter.TclError: unknown option "-number"" error. Any help would be greatly appreciated! Thank you!</p>