lib/Ext/util/Collection.js
function() {
        var me = this,
            copy = new this.self(),
            keys = me.keys,
            items = me.items,
            i = 0,
            ln = items.length;

        for(; i < ln; i++) {
            copy.add(keys[i], items[i]);
        }

        copy.getKey = me.getKey;
        return copy;
    }
function() {
        var me = this,
            copy = new this.self(),
            keys = me.keys,
            items = me.items,
            i = 0,
            ln = items.length;

        for(; i < ln; i++) {
            copy.add(keys[i], items[i]);
        }

        copy.getKey = me.getKey;
        return copy;
    }
Creates a shallow copy of this collection
@return {Ext.util.MixedCollection}