code: def fetch_tweets(account_file, outfile, limit):
      
      print('fetching tweets for accounts in', account_file)
      outf = io.open(outfile, 'wt')
      for screen_name in iter_lines(account_file):
          print('\nFetching tweets for %s' % screen_name)
          for tweet in twutil.collect.tweets_for_user(screen_name, limit):
              tweet['user']['screen_name'] = screen_name
              outf.write('%s\n' % json.dumps(tweet, ensure_ascii=False))
              outf.flush()
docs: Fetch up to limit tweets for each account in account_file and write to
      outfile.