docs: def buttons(self, master):
          '''Add a standard button box.
  
          Override if you do not want the standard buttons
          '''
  
          box = tk.Frame(master)
  
          ttk.Button(
              box,
              text="Next",
              width=10,
              command=self.next_day
          ).pack(side=tk.LEFT, padx=5, pady=5)
          ttk.Button(
              box,
              text="OK",
              width=10,
              command=self.ok,
              default=tk.ACTIVE
          ).pack(side=tk.LEFT, padx=5, pady=5)
          ttk.Button(
              box,
              text="Cancel",
              width=10,
              command=self.cancel
          ).pack(side=tk.LEFT, padx=5, pady=5)
  
          self.bind("n", self.next_day)
          self.bind("<Return>", self.ok)
          self.bind("<Escape>", self.cancel)
  
          box.pack()