docs: function wait_loading(callback) {
  		var undefined,
  		    events = 0,
  		    foreach_loading = true,
  		    errors = [];
  		
  		function do_end() {
  			callback( (errors.length === 0) ? undefined : 'Errors:\n * ' + errors.join(' * \n') );
  		}
  		
  		foreach(_dirs_loading).do(function(e, id) {
  			events++;
  			e.on('end', function(err) {
  				if(err) errors.push(err);
  				events--;
  				if( (!foreach_loading) && (events === 0) ) do_end();
  			});
  		});
  		
  		foreach_loading = false;
  		if(events === 0) do_end();
  	}