function toggle_tree(id) {
    element = document.getElementById(id);

    if (!element) return;
    
    if (element.style.visibility=='visible' || element.style.visibility=='') {
    element.style.visibility = 'hidden';
    element.style.overflow = 'hidden';
    element.style.height=1;

    }
    else {
    element.style.visibility = 'visible';
    element.style.overflow = 'visible';
    element.style.height='';

    }
    
    }
    
    function expand_b(start_id) {
    i = start_id;
    while (1) {
    
    element = document.getElementById(i);

    if (!element) break;
    
    element.style.visibility = '';
    element.style.overflow = 'visible';
    element.style.height='';

    
    i++;
    }
    }
    
    function collapse_b(start_id) {
    i = start_id;
    while (1) {
    
    element = document.getElementById(i);
 
    if (!element) break;
    
    element.style.visibility = 'hidden';
    element.style.overflow = 'hidden';
    element.style.height=1;

    
    i++;
    }
    }