using System.Collections.Generic;

using System.Linq;

using System.Threading.Tasks;

​

public class PlanCapacity

{

}

​

public class HspcStaffing

{

}

​

public class Plan

{

}

​

public class Program

{

    public async void Main()

    {

        var result = await this.BuildPlanStaffingDataAsync(new List<PlanCapacity>(), new Plan());

    }

​

    public virtual async Task<List<List<HspcStaffing>>> BuildPlanStaffingDataAsync(IEnumerable<PlanCapacity> capacity, Plan plan = null)

    {

        return (List<List<HspcStaffing>>)await this.CalculateStaffingAsync(capacity, plan);

    }

​

    public async Task<IEnumerable<HspcStaffing>> CalculateStaffingAsync(IEnumerable<PlanCapacity> capacity, Plan plan)

    {

        return await Task.FromResult(Enumerable.Empty<HspcStaffing>());

    }

}