title: Python tkinter - successfully inherit from toplevel
body: <p>I am trying to use an object-oriented approach to create a class that inherits from tkinter's Toplevel, triggered by pressing a button in the main window.</p>
  
  <p>The current code raises an AttributeError ('MakeWindow' object has no attribute 'tk'). Can anyone point me in the right direction?</p>
  
  <pre><code>#! python3
  import tkinter as tk
  
  
  class Application:
      def __init__(self, master):
          self.frame = tk.Frame(master)
          self.frame.pack()    
          self.okButton = tk.Button(self.frame, text="OK",
                                    command=self.window_maker).pack()
          self.quitButton = tk.Button(self.frame, text="Close",
                                      command=self.frame.quit).pack()
      def window_maker(self):
          MakeWindow("A message to Toplevel")
  
  
  class MakeWindow(tk.Toplevel):
      def __init__(self, message):
          super().__init__(self)
          self.message = message
          self.display = tk.Label(self, text=message)
          self.display.pack()
  
  
  if __name__ == '__main__':
      root = tk.Tk()
      app = Application(root)
      root.mainloop()
  </code></pre>
  
  <p>Full traceback:</p>
  
  <pre><code>Exception in Tkinter callback
  Traceback (most recent call last):
    File "C:\Users\r\AppData\Local\Programs\Python\Python35\lib\tkinter\__init__.py", line 1550, in __call__
      return self.func(*args)
    File "C:/Users/r/PycharmProjects/tkinter_gui/y.py", line 15, in window_maker
      MakeWindow("A message to Toplevel")
    File "C:/Users/r/PycharmProjects/tkinter_gui/y.py", line 20, in __init__
      super().__init__(self)
    File "C:\Users\r\AppData\Local\Programs\Python\Python35\lib\tkinter\__init__.py", line 2182, in __init__
      BaseWidget.__init__(self, master, 'toplevel', cnf, {}, extra)
    File "C:\Users\r\AppData\Local\Programs\Python\Python35\lib\tkinter\__init__.py", line 2132, in __init__
      BaseWidget._setup(self, master, cnf)
    File "C:\Users\r\AppData\Local\Programs\Python\Python35\lib\tkinter\__init__.py", line 2110, in _setup
      self.tk = master.tk
  AttributeError: 'MakeWindow' object has no attribute 'tk'
  </code></pre>