While you're looking at the collections module, look at inheriting from Sequence, Mapping or An additional summary foundation class if that is certainly more acceptable. Here's an example for the Sequence subclass: kmario23kmario23 62k1717 gold badges172172 silver badges159159 bronze badges 2 two Yes, I feel we know why self is https://self-adhesiveminitrunking01234.blogtov.com/17858475/accessory-boxes-fundamentals-explained