code: public static <K, V> ScanIterator<K> scan(RedisKeyCommands<K, V> commands) {
          return scan(commands, Optional.empty());
      }
docs: Sequentially iterate over keys in the keyspace. This method uses {@code SCAN} to perform an iterative scan.
  
  @param commands the commands interface, must not be {@literal null}.
  @param <K> Key type.
  @param <V> Value type.
  @return a new {@link ScanIterator}.