flatten_shorttree = function(tree){
        /**
         * Flatten a tree of shortcut sequences. 
         * use full to iterate over all the key/values of available shortcuts.
         **/
        var  dct = {};
        for(var key in tree){
            var value = tree[key];
            if(typeof(value) === 'string'){
                dct[key] = value;
            } else {
                var ftree=flatten_shorttree(value);
                for(var subkey in ftree){
                    dct[key+','+subkey] = ftree[subkey];
                }
            } 
        }
        return dct;
    }
clear the pending shortcut sequence now.