Generate query parameters for the prev page

def prev(self):
        """ Generate query parameters for the prev page """

        if self.total:
            if self.offset - self.limit - self.limit < 0:
                return self.first
            else:
                offset = self.offset - self.limit
                return {'page[offset]': offset, 'page[limit]': self.limit}
        else:
            return None