public object?GetNthMask(int index)
            {
                PexObjectFunctionInstruction_FieldIndex enu = (PexObjectFunctionInstruction_FieldIndex)index;

                switch (enu)
                {
                case PexObjectFunctionInstruction_FieldIndex.OpCode:
                    return(OpCode);

                case PexObjectFunctionInstruction_FieldIndex.Arguments:
                    return(Arguments);

                default:
                    throw new ArgumentException($"Index is out of range: {index}");
                }
            }
            public void SetNthMask(int index, object obj)
            {
                PexObjectFunctionInstruction_FieldIndex enu = (PexObjectFunctionInstruction_FieldIndex)index;

                switch (enu)
                {
                case PexObjectFunctionInstruction_FieldIndex.OpCode:
                    this.OpCode = (Exception?)obj;
                    break;

                case PexObjectFunctionInstruction_FieldIndex.Arguments:
                    this.Arguments = (MaskItem <Exception?, IEnumerable <MaskItem <Exception?, PexObjectVariableData.ErrorMask?> >?>)obj;
                    break;

                default:
                    throw new ArgumentException($"Index is out of range: {index}");
                }
            }