input: Write a function to create a main window with two buttons using tkinter. One button should open a new window with a "Click me" button, and the other should close the main window.
  assert isinstance(create_main_window(), tkinter.Tk)
  assert isinstance(create_main_window().winfo_children()[0], tkinter.Button)
  assert isinstance(create_main_window().winfo_children()[1], tkinter.Button)
output: def create_main_window():
      import tkinter as tk
      
      def open_new_window():
          new_window = tk.Toplevel(main_window)
          tk.Button(new_window, text="Click me").pack()
      
      main_window = tk.Tk()
      button1 = tk.Button(main_window, text="Open New Window", command=open_new_window)
      button1.pack()
      
      button2 = tk.Button(main_window, text="Close", command=main_window.destroy)
      button2.pack()
      
      return main_window