code: def search_by_category(self, category_id, limit=0, order_by=None, sort_order=None, filter=None):
          url = "%s/category/series?category_id=%d&" % (self.root_url,
                                                        category_id)
          info = self.__get_search_results(url, limit, order_by, sort_order, filter)
          if info is None:
              raise ValueError('No series exists for category id: ' + str(category_id))
          return info