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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:
 async def process_feed(self, url, send_mentions=True):
 """ process a feed """


        self._feed_domains.add(utils.get_domain(url))

        if url in self._processed_feeds:
            LOGGER.debug("Skipping already processed feed %s", url)
            return
        self._processed_feeds.add(url)

        LOGGER.debug("++WAIT: %s: get feed", url)
        feed, previous, updated = await feeds.get_feed(self, url)
        LOGGER.debug("++DONE: %s: get feed", url)

        if updated:
            LOGGER.info("Feed %s has been updated", url)

        if not feed:
            return

        LOGGER.debug("--- starting process_feed %s %s", url, send_mentions)

        pending = []

        try:
            for link in feed.links:
                href = link['href']
                if not href:
                    continue

                #  RFC5005 archive links
                if self.args.archive and link.get('rel') in ('prev-archive',
                                                             'next-archive',
                                                             'prev-page',
                                                             'next-page'):
                    LOGGER.debug("Found archive link %s", link)
                    pending.append(
                        ("process feed " + href, self.process_feed(href, send_mentions)))

                # WebSub notification
                if updated and link.get('rel') == 'hub' and not feed.is_archive:
                    LOGGER.debug("Found WebSub hub %s", link)
                    pending.append(
                        ("update websub " + href, feed.update_websub(self, href)))
        except (AttributeError, KeyError):
            LOGGER.debug("Feed %s has no links", url)

        # Schedule the entries
        items = set(feed.entry_links)
        if previous:
            items |= set(previous.entry_links)
        for entry in items:
            pending.append(("process entry " + entry,
                            self.process_entry(entry, send_mentions=send_mentions)))

        LOGGER.debug("--- finish process_feed %s %s", url, send_mentions)

        if pending:
            LOGGER.debug("+++WAIT: process_feed(%s): %d subtasks",
                         url, len(pending))
            LOGGER.debug("%s", [name for (name, _) in pending])
            await asyncio.wait([task for (_, task) in pending])
            LOGGER.debug("+++DONE: process_feed(%s): %d subtasks",
                         url, len(pending))