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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 download_stories(self, userids: Optional[List[Union[int, Profile]]] = None, fast_update: bool = False, filename_target: Optional[str] = ':stories', storyitem_filter: Optional[Callable[[StoryItem], bool]] = None) -> None: """ Download available stories from user followees or all stories of users whose ID are given. Does not mark stories as seen. To use this, one needs to be logged in :param userids: List of user IDs or Profiles to be processed in terms of downloading their stories :param fast_update: If true, abort when first already-downloaded picture is encountered :param filename_target: Replacement for {target} in dirname_pattern and filename_pattern or None if profile name should be used instead :param storyitem_filter: function(storyitem), which returns True if given StoryItem should be downloaded """


        if not userids:
            self.context.log("Retrieving all visible stories...")
        else:
            userids = [p if isinstance(p, int) else p.userid for p in userids]

        for user_story in self.get_stories(userids):
            name = user_story.owner_username
            self.context.log("Retrieving stories from profile {}.".format(name))
            totalcount = user_story.itemcount
            count = 1
            for item in user_story.get_items():
                if storyitem_filter is not None and not storyitem_filter(item):
                    self.context.log("<{} skipped>".format(item), flush=True)
                    continue
                self.context.log("[%3i/%3i] " % (count, totalcount), end="", flush=True)
                count += 1
                with self.context.error_catcher('Download story from user {}'.format(name)):
                    downloaded = self.download_storyitem(item, filename_target if filename_target else name)
                    if fast_update and not downloaded:
                        break