Mage2\User\Module::registerAdminMenu PHP Method

    public function registerAdminMenu()
    {
        $adminUserMenu = ['user' => ['label' => 'Users', 'route' => '#', 'submenu' => ['admin-users' => ['label' => 'Admin Users', 'route' => 'admin.admin-user.index'], 'roles' => ['label' => 'Roles', 'route' => 'admin.role.index']]]];
        AdminMenu::registerMenu('mage2-user', $adminUserMenu);
    }