Getting back to that init function, there's really quite a bit to it, isn't there?
You're passing 4 parameters:
item, color, shine, bump

One of those parameters (the first one) is going to define an object, and the other three parameters are actually going to be members of this object:
        item.color = color
        item.shine = shine
        item.bump = bump

With these three statements, you actually assign those parameters to the object as members of that object?

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks