code: async def filter_new_posts(self, source_id, post_ids):
          
          new_ids = []
          try:
              db_client = self._db
              posts_in_db = await db_client.get_known_posts(source_id, post_ids)
              new_ids = [p for p in post_ids if p not in posts_in_db]
          except Exception as exc:
              logger.error("Error when filtering for new posts {} {}".format(source_id, post_ids))
              logger.exception(exc)
          return new_ids
docs: Filters ist of post_id for new ones.
  
          :param source_id: id of the source
          :type string:
          :param post_ids: list of post ids
          :type list:
          :returns: list of unknown post ids.