code: def last(limit=1, offset=0)
        from    = offset
        to      = from + limit - 1
        members = redis.zrange(index_key_for(:id), (to * -1) + -1, (from * -1) + -1).reverse
  
        find(limit > 1 ? members : members.first)
      end
docs: Find the first saved record
   @note `last` uses a sorted set as an index of `ids` and finds the highest id.
   @param limit [Integer] returns one or many
   @param offset [Integer] from the end of the index, back
   @return [Base, Array]