def METHOD_NAME(self):
    # Download pre-built CACM index built using Lucene 9; append a random value to avoid filename clashes.
    r = randint(0, 10000000)
    self.collection_url = 'https://github.com/castorini/anserini-data/raw/master/CACM/lucene9-index.cacm.tar.gz'
    self.tarball_name = 'lucene-index.cacm-{}.tar.gz'.format(r)
    self.index_dir = 'index{}/'.format(r)
    filename, headers = urlretrieve(self.collection_url, self.tarball_name)
    tarball = tarfile.open(self.tarball_name)
    tarball.extractall(self.index_dir)
    tarball.close()
    self.searcher = LuceneSearcher(f'{self.index_dir}lucene9-index.cacm')