docs: def _nodup_filter(self, min_hash, all_urls, max_sample=200):
          """ This filters results that are considered not duplicates.
          But we really need to check that, because lsh.query does not always
          return ALL duplicates, esp. when there are a lot of them, so
          here we double-check and return only urls that are NOT duplicates.
          Return estimated number of not duplicates.
          """
          if not all_urls:
              return 0
          urls = random.sample(all_urls, max_sample) \
                 if len(all_urls) > max_sample else all_urls
          filtered = [
              url for url in urls
              if min_hash.jaccard(self.seen_urls[url].min_hash) <
              self.jaccard_threshold]
          return int(len(filtered) / len(urls) * len(all_urls))