def index(self, item):
        """
        Map *item* to an integer representing its zero-based position in this
        slide collection. Raises |ValueError| if *item* is not a slide in
        this collection.
        """
        item_id = id(item)
        for idx, slide in enumerate(self):
            if id(slide) == item_id:
                return idx
        raise ValueError(item % '%s is not in slide collection')
dataset/ETHPy150Open scanny/python-pptx/pptx/parts/presentation.py/_Slides.index/swapped operands of `%`