protected function coursecat_tree(coursecat_helper $chelper, $coursecat) {
        // Reset the category expanded flag for this course category tree first.
        $this->categoryexpandedonload = false;
        $categorycontent = $this->coursecat_category_content($chelper, $coursecat, 0);
        if (empty($categorycontent)) {
            return '';
        }

        // Start content generation
        $content = '';
        $attributes = $chelper->get_and_erase_attributes('course_category_tree clearfix');
        $content .= html_writer::start_tag('div', $attributes);

        if ($coursecat->get_children_count()) {
            $classes = array(
                'collapseexpand',
            );

            // Check if the category content contains subcategories with children's content loaded.
            if ($this->categoryexpandedonload) {
                $classes[] = 'collapse-all';
                $linkname = get_string('collapseall');
            } else {
                $linkname = get_string('expandall');
            }

            // Only show the collapse/expand if there are children to expand.
            $content .= html_writer::start_tag('div', array('class' => 'collapsible-actions'));
            $content .= html_writer::link('#', $linkname, array('class' => implode(' ', $classes)));
            $content .= html_writer::end_tag('div');
            $this->page->requires->strings_for_js(array('collapseall', 'expandall'), 'moodle');
        }

        $content .= html_writer::tag('div', $categorycontent, array('class' => 'content'));

        $content .= html_writer::end_tag('div'); // .course_category_tree

        return $content;
    }