code: def previous_page(self):
          
          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 ""
docs: Return URL for previous page.
  
          :return str: