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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def collections(self, username, page=1, per_page=10):
 """ 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. """

        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)