code: @Override
    public Long scard(final byte[] key) {
      checkIsInMultiOrPipeline();
      client.scard(key);
      return client.getIntegerReply();
    }
docs: Return the set cardinality (number of elements). If the key does not exist 0 is returned, like
  for empty sets.
  @param key
  @return Integer reply, specifically: the cardinality (number of elements) of the set as an
  integer.