code: def collections(self, username, page=1, per_page=10):
          
          url = "/users/{username}/collections".format(username=username)
          params = {
              "page": page,
              "per_page": per_page
          }
          result = self._get(url, params=params)
          return CollectionModel.parse_list(result)
docs: Get a list of collections created by the 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)
          :return: [Array]: A single page of the Collection list.