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Solve the following problem using Python, implementing the functions described below, one line at a time
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<USER_TASK:>
Description:
 def get_user_submissions(self, task):
 """ Get all the user's submissions for a given task """

        if not self._user_manager.session_logged_in():
            raise Exception("A user must be logged in to get his submissions")

        cursor = self._database.submissions.find({"username": self._user_manager.session_username(),
                                                  "taskid": task.get_id(), "courseid": task.get_course_id()})
        cursor.sort([("submitted_on", -1)])
        return list(cursor)