create complex attribute as output

[mpGroup]

create complex attribute,

Hi! I have three types of attributes, such as kDynArrayAttrs, kNurbsCurve, and point Position, as shown in the picture below. Now, I want to have a single attribute, for example, an ' outParameterst' attribute, that can store NurbsCurve, point Position, and a doubleArray together. Or, in general, I want to have a single output attribute that can store multiple types of data, such as NurbsCurve, Float, and PointArray.
C++ Api, thanks.