I haven’t tested this in .ghpy but I’d try either
instance.Exposure = Grasshopper.Kernel.GH_Exposure.primary
somewhere in the constructor

(referenced from here Tutorial: creating a Grasshopper component with the Python GHPY compiler )
Or it is a function override like such:
def Exposure(self):
return Grasshopper.Kernal.GH_Exposure.primary
primary means the first group, secondary the second and so on. They are separated by the divider you’re looking for.