<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def related(self, collection_id):
 """ Retrieve a list of collections related to this one. :param collection_id [string]: The collection’s ID. Required. :return: [Array]: A single page of the Collection list. """

        url = "/collections/%s/related" % collection_id
        result = self._get(url)
        return CollectionModel.parse_list(result)