code: def __init__(self, grammar, text):
      self._grammar = grammar
      self._text = text
  
      # Set up the main window.
      self._top = Tk()
      self._top.title("Context Free Grammar Demo")
  
      # Base font size
      self._size = IntVar(self._top)
      self._size.set(12)  # = medium
  
      # Set up the key bindings
      self._init_bindings(self._top)
  
      # Create the basic frames
      frame1 = Frame(self._top)
      frame1.pack(side="left", fill="y", expand=0)
      self._init_menubar(self._top)
      self._init_buttons(self._top)
      self._init_grammar(frame1)
      self._init_treelet(frame1)
      self._init_workspace(self._top)
  
imports: import re
  from tkinter import Button, Canvas, Entry, Frame, IntVar, Label, Scrollbar, Text, Tk, Toplevel
  from nltk.draw.tree import TreeSegmentWidget, tree_to_treesegment
  from nltk.draw.util import CanvasFrame, ColorizedList, ShowText, SymbolWidget, TextWidget
  from nltk.grammar import CFG, Nonterminal, _read_cfg_production, nonterminals
  from nltk.tree import Tree
label_desc: Use image node_id 1 to create a new CFGDemo object  with example: obj = CFGDemo(grammar, text)