Return the slide identified by integer *slide_id* in this
        presentation, or *default* if not found.

def get(self, slide_id, default=None):
        """
        Return the slide identified by integer *slide_id* in this
        presentation, or *default* if not found.
        """
        slide = self.part.get_slide(slide_id)
        if slide is None:
            return default
        return slide