code: def _update_defaults(self, defaults, old_version, verbose=False):
          
          old_defaults = self._load_old_defaults(old_version)
          for section, options in defaults:
              for option in options:
                  new_value = options[ option ]
                  try:
                      old_value = old_defaults.get(section, option)
                  except (cp.NoSectionError, cp.NoOptionError):
                      old_value = None
                  if old_value is None or \
                    to_text_string(new_value) != old_value:
                      self._set(section, option, new_value, verbose)
docs: Update defaults after a change in version