code: def test_callback_backward_index(self):
      def myreplace(exc):
          if myreplace.limit > 0:
              myreplace.limit -= 1
              return ("REPLACED", 0)
          else:
              return ("TERMINAL", exc.end)
  
      myreplace.limit = 3
      codecs.register_error("test.cjktest", myreplace)
      self.assertEqual(
          self.encode(
              "abcd" + self.unmappedunicode + "efgh", "test.cjktest"
          ),
          (b"abcdREPLACEDabcdREPLACEDabcdREPLACEDabcdTERMINALefgh", 9),
      )
  
imports: import codecs
  import os
  import re
  import sys
  import unittest
  from http.client import HTTPException
  from test import support
  from io import BytesIO
label_desc: Use image node_id 10 for calling the TestBase obj's underlying member method code with example usage: obj.test_callback_backward_index() and returns: str,  int, str,  exc