code: def _init_grammar(self, parent):
      self._prodlist = ProductionList(parent, self._grammar, width=20)
      self._prodlist.pack(side="top", fill="both", expand=1)
      self._prodlist.focus()
      self._prodlist.add_callback("select", self._selectprod_cb)
      self._prodlist.add_callback("move", self._selectprod_cb)
  
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 5 for calling the CFGDemo obj's underlying member method code with example usage: obj._init_grammar(parent) without return types