class SessionStateEmpty implements SessionState{

    private Map<String,Object> sessionMap = null;
    public Map<String,Object> sessionMap(){<FILL_FUNCTION_BODY>}

    @Override
    public String sessionId() {
        return null;
    }

    @Override
    public String sessionChangeId() {
        return null;
    }

    @Override
    public Collection<String> sessionKeys() {
        return sessionMap().keySet();
    }

    @Override
    public <T> T sessionGet(String key, Class<T> clz) {
        return (T)sessionMap().get(key);
    }

    @Override
    public void sessionSet(String key, Object val) {
        if (val == null) {
            sessionRemove(key);
        } else {
            sessionMap().put(key, val);
        }
    }

    @Override
    public void sessionRemove(String key) {
        sessionMap().remove(key);
    }

    @Override
    public void sessionClear() {
        sessionMap().clear();
    }

    @Override
    public void sessionReset() {
        sessionMap().clear();
    }
}

        if(sessionMap == null){
            sessionMap = new HashMap<>();
        }

        return sessionMap;
    
<no_super_class>