code: def set_cntx_bf_len(self, **kwargs):
      self._char_before = self._cntx_bf_len.get()
  
imports: import queue
  import re
  import threading
  from tkinter import END, LEFT, SUNKEN, Button, Entry, Frame, IntVar, Label, Menu, OptionMenu, Scrollbar, StringVar, Text, Tk
  from tkinter.font import Font
  from nltk.corpus import alpino, brown, cess_cat, cess_esp, floresta, indian, mac_morpho, nps_chat, sinica_treebank, treebank
  from nltk.draw.util import ShowText
  from nltk.util import in_idle
label_desc: Use image node_id 7 for calling the ConcordanceSearchView obj's underlying member method code with example usage: obj.set_cntx_bf_len() without return types