I can't sort items out of group

I have a table like the one below, I have items outside groups and 1 group, I can get items that are inside group and put outside this group but I can't get items and add to group, how to add items to group?
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The HTML:
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A Column




A Item 1


A Item 2


A Item 3


A Item 4


A Item 5



A Item 5.1


A Item 5.2


A Item 5.3


A Item 5.4






A Item 6

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The JavaScript

>

>

>

> $(function () {
> $('.sorted_table').sortable({
> containerSelector: 'table',
> itemPath: '> tbody',
> itemSelector: 'tr',
> placeholder: '<tr class="placeholder"/>'
> });
> });

>

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