- (NSString *)operationDefinition{
    return [NSString stringWithFormat:
            @"query getListCollection{"
            "   collectionOfCategory(category_id:%d,page: %d, where: %@) {"
             "       data {"
             "           name"
             "           id"
             "           description"
             "           image"
             "           classes {"
             "               id"
             "               name"
             "               image"
             "               video_url"
             "           }"
             "       }"
             "   }"
            "}",self.idCategory, 1, @"null"];
}