toJSON() {
        return {
            filters: this.filters.map(f => f.toJSON()),
            op: this.op
        };
    }
/** Outputs JSON appropriate for recreation via `parseFilter` */
Outputs JSON appropriate for recreation via `parseFilter`
Outputs JSON appropriate for recreation via ` parseFilter `
toJSON() {
        return {
            filters: this.filters.map(f => f.toJSON()),
            op: this.op
        };
    }
toJSON ( ) { return { filters : this . filters . map ( f => f . toJSON ( ) ) , op : this . op } ; }
Outputs JSON appropriate for recreation via `parseFilter`
Outputs JSON appropriate for recreation via ` parseFilter `