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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _watch_and_update(self):
 """ Keeps the current list of resources up-to-date This method is to be run not on the main thread! We first fetch the list of current resources, and store that. Then we register to be notified of changes to those resources, and keep our local store up-to-date based on these notifications. We also perform exponential backoff, giving up after we hit 32s wait time. This should protect against network connections dropping and intermittent unavailability of the api-server. Every time we recover from an exception we also do a full fetch, to pick up changes that might've been missed in the time we were not doing a watch. Note that we're playing a bit with fire here, by updating a dictionary in this thread while it is probably being read in another thread without using locks! However, dictionary access itself is atomic, and as long as we don't try to mutate them (do a 'fetch / modify / update' cycle on them), we should be ok! """

        selectors = []
        log_name = ""
        if self.label_selector:
            selectors.append("label selector=%r" % self.label_selector)
        if self.field_selector:
            selectors.append("field selector=%r" % self.field_selector)
        log_selector = ', '.join(selectors)

        cur_delay = 0.1

        self.log.info(
            "watching for %s with %s in namespace %s",
            self.kind, log_selector, self.namespace,
        )
        while True:
            self.log.debug("Connecting %s watcher", self.kind)
            start = time.monotonic()
            w = watch.Watch()
            try:
                resource_version = self._list_and_update()
                if not self.first_load_future.done():
                    # signal that we've loaded our initial data
                    self.first_load_future.set_result(None)
                watch_args = {
                    'namespace': self.namespace,
                    'label_selector': self.label_selector,
                    'field_selector': self.field_selector,
                    'resource_version': resource_version,
                }
                if self.request_timeout:
                    # set network receive timeout
                    watch_args['_request_timeout'] = self.request_timeout
                if self.timeout_seconds:
                    # set watch timeout
                    watch_args['timeout_seconds'] = self.timeout_seconds
                # in case of timeout_seconds, the w.stream just exits (no exception thrown)
                # -> we stop the watcher and start a new one
                for ev in w.stream(
                        getattr(self.api, self.list_method_name),
                        **watch_args
                ):
                    cur_delay = 0.1
                    resource = ev['object']
                    if ev['type'] == 'DELETED':
                        # This is an atomic delete operation on the dictionary!
                        self.resources.pop(resource.metadata.name, None)
                    else:
                        # This is an atomic operation on the dictionary!
                        self.resources[resource.metadata.name] = resource
                    if self._stop_event.is_set():
                        self.log.info("%s watcher stopped", self.kind)
                        break
                    watch_duration = time.monotonic() - start
                    if watch_duration >= self.restart_seconds:
                        self.log.debug(
                            "Restarting %s watcher after %i seconds",
                            self.kind, watch_duration,
                        )
                        break
            except ReadTimeoutError:
                # network read time out, just continue and restart the watch
                # this could be due to a network problem or just low activity
                self.log.warning("Read timeout watching %s, reconnecting", self.kind)
                continue
            except Exception:
                cur_delay = cur_delay * 2
                if cur_delay > 30:
                    self.log.exception("Watching resources never recovered, giving up")
                    if self.on_failure:
                        self.on_failure()
                    return
                self.log.exception("Error when watching resources, retrying in %ss", cur_delay)
                time.sleep(cur_delay)
                continue
            else:
                # no events on watch, reconnect
                self.log.debug("%s watcher timeout", self.kind)
            finally:
                w.stop()
                if self._stop_event.is_set():
                    self.log.info("%s watcher stopped", self.kind)
                    break
        self.log.warning("%s watcher finished", self.kind)