protected function get_filters_as_booleans() {
        $filters = [
            BLOCK_TIMELINE_FILTER_BY_NONE => false,
            BLOCK_TIMELINE_FILTER_BY_OVERDUE => false,
            BLOCK_TIMELINE_FILTER_BY_7_DAYS => false,
            BLOCK_TIMELINE_FILTER_BY_30_DAYS => false,
            BLOCK_TIMELINE_FILTER_BY_3_MONTHS => false,
            BLOCK_TIMELINE_FILTER_BY_6_MONTHS => false
        ];

        // Set the selected filter to true.
        $filters[$this->filter] = true;

        return $filters;
    }