private function get_default_tree_structure() {

        $frontpage = \context_course::instance(SITEID);

        $categorybranches = $this->get_all_category_branches();

        $elements = [
            'text' => get_string('contextlevelname' . CONTEXT_SYSTEM, 'tool_dataprivacy'),
            'contextlevel' => CONTEXT_SYSTEM,
            'branches' => [
                [
                    'text' => get_string('user'),
                    'contextlevel' => CONTEXT_USER,
                ], [
                    'text' => get_string('categories'),
                    'branches' => $categorybranches,
                    'expandelement' => 'category',
                ], [
                    'text' => get_string('frontpagecourse', 'tool_dataprivacy'),
                    'contextid' => $frontpage->id,
                    'branches' => [
                        [
                            'text' => get_string('activitiesandresources', 'tool_dataprivacy'),
                            'expandcontextid' => $frontpage->id,
                            'expandelement' => 'module',
                            'expanded' => 0,
                        ], [
                            'text' => get_string('blocks'),
                            'expandcontextid' => $frontpage->id,
                            'expandelement' => 'block',
                            'expanded' => 0,
                        ],
                    ]
                ]
            ]
        ];

        // Returned as an array to follow a common array format.
        return [self::complete($elements, $this->defaultcontextlevel, $this->defaultcontextid)];
    }