Question about Baking Method in GH Component VB.NET

Can someone give me a quick overview of the bake method in GH?

Say I have a GH_Point object, some psedueo code;

Dim ghPoint As New Grasshopper.Kernel.Types.GH_Point

ghPoint.SetPoint(25.0, 0.0, 25.0)

For baking we use the method

ghPoint.BakeGeometry (doc,att,obj_guid,obj_inst)

To use this method the following arguments are needed:

dim doc as MRhinoDocument

dim obj_inst as IRhinoObject

dim obj_guid as System.Guid

dim att as IRhinoObjectAttributes

How do I know the obj_guid if the object doesnt exist until after baking? Shouldnt the baking method automatcially return the guid and obj_inst after execution?

Cheers