Ex: Weapon model attached to Camera
I don't find any thing related to parenting in Document

It doesnt work this way here, you can decide who is parent to other classes.
You can create your custom class with a weapon model and the camera, set it up at creation and update to be at the matrix of the object.

You gotta think that the classes here are very open and can interact with each other if you set it up correctly.

The only big place where you will find parent relationship in those terms is the GUI