creating a tree hierarchy using QStandardModel

[wind]

I have a XML file with the following structure:

<?xml version="1.0" encoding="utf-8"?>
<isl_project_command>
	<task>
		<code>root</code>
		<parent_code></parent_code>
		<start_date>date</start_date>
	</task>
	<task>
		<code>child1</code>
		<parent_code>root</parent_code>
		<start_date>date</start_date>
	</task>
	<task>
		<code>child1.1</code>
		<parent_code>child1</parent_code>
		<start_date>date</start_date>
	</task>
</isl_project_command>

<?xml version="1.0" encoding="utf-8"?>
<isl_project_command>
	<task>
		<code>root</code>
		<parent_code></parent_code>
		<start_date>date</start_date>
	</task>
	<task>
		<code>child1</code>
		<parent_code>root</parent_code>
		<start_date>date</start_date>
	</task>
	<task>
		<code>child1.1</code>
		<parent_code>child1</parent_code>
		<start_date>date</start_date>
	</task>
</isl_project_command>

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Now i try to build a QStandardModel of this structure for displaying data in a QTreeView.
The problem is i don't know how to create a hierarchy tree of the data.

The tree should look something like this: