private ArrayList<HashMap<String, Object>> extractSessions(Object courseId) {
		ArrayList<HashMap<String, Object>> list = new ArrayList<HashMap<String, Object>>();
		ArrayList<Object> remove = new ArrayList<Object>();
		for (Object key : this.sessions.keySet()) {
			HashMap<String, Object> ses = this.sessions.get(key);
			if (courseId.equals(ses.get("courseId"))) {
				list.add(ses);
				remove.add(key);
			}
		}
		for (Object key : remove)
			this.sessions.remove(key);
		return list;
	}