static/ext/src/util/AbstractMixedCollection.js
function() {
        var me = this,
            copy = new this.self(me.initialConfig);

        copy.add(me.keys, me.items);
        return copy;
    }
function() {
        var me = this,
            copy = new this.self(me.initialConfig);

        copy.add(me.keys, me.items);
        return copy;
    }
Creates a shallow copy of this collection
@return {Ext.util.MixedCollection}
@since Ext 1