<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def tree_node_to_xml(self, parent, item):
 """Converts a treeview item and children to xml nodes"""


        tree = self.treeview
        data = self.treedata[item]
        node = data.to_xml_node()

        children = tree.get_children(item)
        for child in children:
            cnode = ET.Element('child')
            cwidget = self.tree_node_to_xml(item, child)
            cnode.append(cwidget)
            node.append(cnode)

        return node