How to use the @js-joda/core.Year.isLeap function in @js-joda/core

_rangeWOWBY(temporal) {
        const sow = this._weekDef.firstDayOfWeek().value();
        const isoDow = temporal.get(ChronoField.DAY_OF_WEEK);
        const dow = MathUtil.floorMod(isoDow - sow, 7) + 1;
        const woy = this._localizedWeekOfYear(temporal, dow);
        if (woy === 0) {
            // TODO: we use IsoChronology for now
            return this._rangeWOWBY(IsoChronology.INSTANCE.date(temporal).minus(2, ChronoUnit.WEEKS));
            // return this._rangeWOWBY(Chronology.from(temporal).date(temporal).minus(2, ChronoUnit.WEEKS));
        }
        const offset = this._startOfWeekOffset(temporal.get(ChronoField.DAY_OF_YEAR), dow);
        const year = temporal.get(ChronoField.YEAR);
        const yearLen = Year.isLeap(year) ? 366 : 365;
        const weekIndexOfFirstWeekNextYear = ComputedDayOfField._computeWeek(offset, yearLen + this._weekDef.minimalDaysInFirstWeek());
        if (woy >= weekIndexOfFirstWeekNextYear) {
            // TODO: we use IsoChronology for now
            return this._rangeWOWBY(IsoChronology.INSTANCE.date(temporal).plus(2, ChronoUnit.WEEKS));
            // return this._rangeWOWBY(Chronology.from(temporal).date(temporal).plus(2, ChronoUnit.WEEKS));
        }
        return ValueRange.of(1, weekIndexOfFirstWeekNextYear - 1);
    }

_localizedWBY(temporal) {
        const sow = this._weekDef.firstDayOfWeek().value();
        const isoDow = temporal.get(ChronoField.DAY_OF_WEEK);
        const dow = MathUtil.floorMod(isoDow - sow, 7) + 1;
        const year = temporal.get(ChronoField.YEAR);
        const woy = this._localizedWeekOfYear(temporal, dow);
        if (woy === 0) {
            return year - 1;
        } else if (woy < 53) {
            return year;
        }
        const offset = this._startOfWeekOffset(temporal.get(ChronoField.DAY_OF_YEAR), dow);
        const yearLen = Year.isLeap(year) ? 366 : 365;
        const weekIndexOfFirstWeekNextYear = ComputedDayOfField._computeWeek(offset, yearLen + this._weekDef.minimalDaysInFirstWeek());
        if (woy >= weekIndexOfFirstWeekNextYear) {
            return year + 1;
        }
        return year;
    }

_localizedWOWBY(temporal) {
        const sow = this._weekDef.firstDayOfWeek().value();
        const isoDow = temporal.get(ChronoField.DAY_OF_WEEK);
        const dow = MathUtil.floorMod(isoDow - sow, 7) + 1;
        const woy = this._localizedWeekOfYear(temporal, dow);
        if (woy === 0) {
            const previous = LocalDate.from(temporal).minus(1, ChronoUnit.WEEKS);
            return this._localizedWeekOfYear(previous, dow) + 1;
        } else if (woy >= 53) {
            const offset = this._startOfWeekOffset(temporal.get(ChronoField.DAY_OF_YEAR), dow);
            const year = temporal.get(ChronoField.YEAR);
            const yearLen = Year.isLeap(year) ? 366 : 365;
            const weekIndexOfFirstWeekNextYear = ComputedDayOfField._computeWeek(offset, yearLen + this._weekDef.minimalDaysInFirstWeek());
            if (woy >= weekIndexOfFirstWeekNextYear) {
                return (woy - (weekIndexOfFirstWeekNextYear - 1));
            }
        }
        return woy;
    }