How can we use EMPTY filter inside an api search link?

Hello Eveyrone,
I am trying to use an API link to query some data on DHIS2.
I know how to use EQ and the other filters within an api link, but can’t figure out how to use EMPTY filter inside an api link.

Here is an example:

https://medair.dhis2.bluesquare.org/api/30/trackedEntityInstances/query.json?ou=someOrgUnitId&ouMode=ACCESSIBLE&program=someProgramId&attribute=qaOqvRz6TNb:EMPTY&paging=false&fields=*

I’ve got an error reply that empty is not a known filter.

So how can I use this filter within the search API?