code: @Override
    public Long sadd(final byte[] key, final byte[]... members) {
      checkIsInMultiOrPipeline();
      client.sadd(key, members);
      return client.getIntegerReply();
    }
docs: Add the specified member to the set value stored at key. If member is already a member of the
  set no operation is performed. If key does not exist a new set with the specified member as
  sole member is created. If the key exists but does not hold a set value an error is returned.
  <p>
  Time complexity O(1)
  @param key
  @param members
  @return Integer reply, specifically: 1 if the new element was added 0 if the element was
  already a member of the set