undefined method `limit_by`

[jbwl]

I am trying to apply a limit_by to my cube. I'm having a hard time figuring out the arguments to pass. My dimension is called product_id, and I want to limit it to 10 results:

I tried:

cube = cube.limit_by(['product_id'],[10]) and cube = cube.limit_by(['product_id',10]) Both fail with: undefined method limit_by for #<Arel::SelectManager>

Looking at the source, I also tried cube = cube.limit_by([{ each: ['productid'],limit: [10]}]) Which also fails with undefined method limit_by for #<Arel::SelectManager>

Could you please give an example how to use the limit_by option?