Does time_bucket_gapfill needs constant start and end?

TimescaleDB and PostgreSQL
1

It is not clear to me from the documentation if the start and finish parameters of the time_bucket_gapfill can only be constant values. When I use time_bucket_gapfill with a time range that is dynamic, I get the following error:

Query 1 ERROR at Line 1: : ERROR:  missing time_bucket_gapfill argument: could not infer start from WHERE clause
HINT:  Specify start and finish as arguments or in the WHERE clause.

This is an example of what I am doing:

select *, metric.value 
from 
	test_table,
	lateral (
            select 
	         time_bucket_gapfill('1d', time) as time,
	         avg(value) as value 
            from metric
            where time >= test_table.time - INTERVAL '1d' and time < NOW()
            group by 1
       ) metric