text: import abc
  import tkinter as tk
  import tkinter.ttk as ttk
  
  
  class NoteBookFrame(ttk.Frame):
      def __init__(self, master: tk.Misc) -> None:
          ttk.Frame.__init__(self, master)
  
      @abc.abstractmethod
      def enter(self):
          raise NotImplementedError()
  
      @abc.abstractmethod
      def leave(self):
          raise NotImplementedError()
  