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?