code: @Override
    public Long ttl(final byte[] key) {
      checkIsInMultiOrPipeline();
      client.ttl(key);
      return client.getIntegerReply();
    }
docs: The TTL command returns the remaining time to live in seconds of a key that has an
  {@link #expire(byte[], int) EXPIRE} set. This introspection capability allows a Redis client to
  check how many seconds a given key will continue to be part of the dataset.
  @param key
  @return Integer reply, returns the remaining time to live in seconds of a key that has an
  EXPIRE. If the Key does not exists or does not have an associated expire, -1 is
  returned.