code: def photos(self, username, page=1, per_page=10, order_by="latest"):
          
          url = "/users/{username}/photos".format(username=username)
          result = self._photos(url, username, page=page, per_page=per_page, order_by=order_by)
          return PhotoModel.parse_list(result)
docs: Get a list of photos uploaded by a user.
  
          :param username [string]: The user’s username. Required.
          :param page [integer]: Page number to retrieve. (Optional; default: 1)
          :param per_page [integer]: Number of items per page. (Optional; default: 10)
          :param order_by [string]: How to sort the photos. Optional.
          (Valid values: latest, oldest, popular; default: latest)
          :return: [Array]: A single page of the Photo list.