Return URL for previous page.

        :return str:

def previous_page(self):
        """ Return URL for previous page.

        :return str:

        """
        if self.page.has_previous():
            previous = self.page.previous_page_number()
            if previous == 1:
                if 'page' in self.query_dict:
                    del self.query_dict['page']
            else:
                self.query_dict['page'] = previous
            return "%s?%s" % (self.path, urlencode(self.query_dict))
        return ""