Filter whether terms should be looked up by ID when filtering posts by taxonomy.
This is useful when filtering taxonomies with numeric slugs by a numeric value (i.e. zip codes). By default, Populate Anything will assume numeric values are term IDs and search by ID with the given value. Use this to indicate that your numeric values are slugs and not IDs.
add_filter( 'gppa_should_get_term_by_id', '__return_false' );