function list_import_prepare()
{
$CI =& get_instance();
$periods = new Period();
$periods->truncate();
echo 'LIST periods table truncated ...' . "\n";
$courses = new Course();
$courses->truncate();
echo 'LIST courses table truncated ...' . "\n";
$groups = new Group();
$groups->truncate();
echo 'LIST groups table truncated ...' . "\n";
$rooms = new Room();
$rooms->truncate();
echo 'LIST rooms table truncated ...' . "\n";
$participants = new Participant();
$participants->truncate();
echo 'LIST participants table truncated ...' . "\n";
$CI->db->simple_query('TRUNCATE TABLE `course_task_set_type_rel`');
echo 'LIST course_task_set_type_rel table truncated ...' . "\n";
$categories = new Category();
$categories->truncate();
echo 'LIST categories table truncated ...' . "\n";
$tasks = new Task();
$tasks->truncate();
$CI->lang->delete_overlays('tasks');
unlink_recursive('private/uploads/task_files/', FALSE);
unlink_recursive('private/uploads/unit_tests/', FALSE);
echo 'LIST tasks table truncated ...' . "\n";
$CI->db->simple_query('TRUNCATE TABLE `task_category_rel`');
echo 'LIST task_category_rel table truncated ...' . "\n";
$task_set_types = new Task_set_type();
$task_set_types->truncate();
echo 'LIST task_set_types table truncated ...' . "\n";
$task_sets = new Task_set();
$task_sets->truncate();
$CI->lang->delete_overlays('task_sets');
echo 'LIST task_sets table truncated ...' . "\n";
$comments = new Comment();
$comments->truncate();
echo 'LIST comments table truncated ...' . "\n";
$solutions = new Solution();
$solutions->truncate();
unlink_recursive('private/uploads/solutions/', FALSE);
echo 'LIST solutions table truncated ...' . "\n";
$CI->db->simple_query('TRUNCATE TABLE `task_task_set_rel`');
echo 'LIST task_task_set_rel table truncated ...' . "\n";
}