Problem with show subcategory images on menui

[Ariseweb]

Hi my theme uses tmmegamenu. I want to show the subcategory images but i cant find the solution. I know that i have to modify this function:

 protected function generateCategoriesMenu($categories)
    {
        $html = '';

        foreach ($categories as $category) {
            if ($category['level_depth'] > 1) {
                $cat = new Category($category['id_category']);
                $link = Tools::HtmlEntitiesUTF8($cat->getLink());
                
            } else {
                $link = $this->context->link->getPageLink('index');
            }

            $html .= '<li'.(($this->page_name == 'category'
                && (int)Tools::getValue('id_category') == (int)$category['id_category']) ? ' class="sfHoverForce category"' : ' class="category"').'>';
            $html .= '<img class="foto_categorias" src="';
            $html .= $foto;
            $html .= '">';
            $html .= '<a href="'.$link.'" title="'.$category['name'].'">'.$category['name'].'</a>';

            if (isset($category['children']) && !empty($category['children'])) {
                $html .= '<ul>';
                    $html .= $this->generateCategoriesMenu($category['children'], 1);
                $html .= '</ul>';
            }

            $html .= '</li>';
        }

        return $html;
    }

I created the variable $fotos to create the src of the image, but i cant find the function or class to do it. Can you help me please ??