Vespa query filter - how to check whether a specific int is in a document's int array field

What's the proper way to check whether an integer is inside an array field when filtering in a Vespa query?

Given the following field in a document:

field location_ids type array<int> {    indexing: summary | attribute}

I want to filter documents that contain a specific integer ID:

{'yql': 'SELECT * FROM doc WHERE userQuery() AND <int X in location_ids>','query': 'some query text'}

I'm not sure how to do this with an int array, as the docs and project examples dealt mainly with string arrays.

Any help appreciated!