Class 'vB_Api_Extensions' not found

Hello,
I have another one and I need your help.
I created a mode for my forum (vb5). I used ajax to transfer data from outside to core/packages/helloworld/api/page.php:

[php]<?php
class helloworld_Api_Page extends vB_Api_Extensions
{
public $product = 'helloworld';
public $version = '1.0.0';
public $developer = 'Bkav';
public $title = 'New Home';
public $minver = ........

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Class 'vB_Api_Extensions' not found