def start_index(self):
        """Return the 1-based index of the first item on this page."""
        paginator = self.paginator
        # Special case, return zero if no items.
        if paginator.count == 0:
            return 0
        elif self.number == 1:
            return 1
        return (
            (self.number - 2) * paginator.per_page + paginator.first_page + 1)
Return the 1-based index of the first item on this page.