edx-platform/cms/static/js/models/xblock_container_info.js

define(['js/models/custom_sync_xblock_info'],
    function(CustomSyncXBlockInfo) {
        var XBlockContainerInfo = CustomSyncXBlockInfo.extend({
            urlRoots: {
                read: '/xblock/container'
            }
        });
        return XBlockContainerInfo;
    });