Clarification Required for the Use of "if not is_last:" Condition

[Waybaba]

https://github.com/jannerm/diffuser/blob/7ea422860cc0106e5ca5949d980f04b799d5462c/diffuser/models/temporal.py#L89C4-L89C4

Dear Maintainers,

I was examining the line of code at this location: Link and came across the conditional statement if not is_last:. Given that each block halves the horizon, I'm wondering if this if statement is necessary.

When I attempted to integrate the code with maze2d, it appeared that the code runs only upon removal of this line. Could you provide some insight into its function and why it might be necessary in the current implementation?

I appreciate your guidance on this issue. Thank you.

Best Regards.