code: @Override
    public Long sdiffstore(final byte[] dstkey, final byte[]... keys) {
      checkIsInMultiOrPipeline();
      client.sdiffstore(dstkey, keys);
      return client.getIntegerReply();
    }
docs: This command works exactly like {@link #sdiff(byte[]...) SDIFF} but instead of being returned
  the resulting set is stored in dstkey.
  @param dstkey
  @param keys
  @return Status code reply