code: def bucket_lister(bucket, prefix='', delimiter='', marker='', headers=None):
      
      more_results = True
      k = None
      while more_results:
          rs = bucket.get_all_keys(prefix=prefix, marker=marker,
                                   delimiter=delimiter, headers=headers)
          for k in rs:
              yield k
          if k:
              marker = rs.next_marker or k.name
          more_results= rs.is_truncated
docs: A generator function for listing keys in a bucket.