How to use the fabric-contract-api.Param function in fabric-contract-api

const vehicle = await ctx.vehicleList.get(vin);

        if (organization instanceof Manufacturer && !vehicle.madeByOrg(participant.orgId)) {
            throw new Error('Manufacturers may only get a vehicle produced by their organisation');
        }

        // DON'T LIMIT THE INSURER AS WHEN GIVEN A VIN AS PART OF A REQUEST THEY NEED TO SEE THE CAR
        // REMEMBER READ ACCESS CONTROL IN HERE IS JUST AS ITS USEFUL TO THE ORGANISATION IT LIMITS.
        // THEY COULD GET FULL DATA IF THEY WISH AS NO DATA IS PRIVATE

        return vehicle;
    }

    @Transaction()
    @Param('endDate', 'number', 'end date as timestamp in seconds')
    @Returns('Policy')
    public async createPolicy(
        ctx: VehicleManufactureNetContext, vin: string, holderId: string, policyType: PolicyType, endDate: number,
    ): Promise {
        const { participant } = ctx.clientIdentity;

        if (!participant.hasRole(Roles.POLICY_CREATE)) {
            throw new Error(`Only callers with role ${Roles.POLICY_CREATE} can create policies`);
        }

        const vehicle = await ctx.vehicleList.get(vin);

        if (vehicle.vehicleStatus !== VehicleStatus.ACTIVE) {
            throw new Error('Cannot insure vehicle which is not active');
        }