code: def char_diff(self, old, new):
          
          def color_transition(old_type, new_type):
              new_color = termcolor.colored("", None, "on_red" if new_type ==
                                            "-" else "on_green" if new_type == "+" else None)
              return "{}{}".format(termcolor.RESET, new_color[:-len(termcolor.RESET)])
  
          return self._char_diff(old, new, color_transition)
docs: Return color-coded character-based diff between `old` and `new`.