Merge xml files with nested elements without external libraries

I am trying to merge multiple XML files together using Python and no external libraries. The XML files have nested elements.

Sample File 1:

<root><element1>textA</element1><elements><nested1>text now</nested1></elements></root>

Sample File 2:

<root><element2>textB</element2><elements><nested1>text after</nested1><nested2>new text</nested2></elements></root>

What I Want:

<root><element1>textA</element1>    <element2>textB</element2>  <elements><nested1>text after</nested1><nested2>new text</nested2></elements>  </root>  

What I have tried:

From this answer.

from xml.etree import ElementTree as etdef combine_xml(files):    first = None    for filename in files:        data = et.parse(filename).getroot()        if first is None:            first = data        else:            first.extend(data)    if first is not None:        return et.tostring(first)

What I Get:

<root><element1>textA</element1><elements><nested1>text now</nested1></elements><element2>textB</element2><elements><nested1>text after</nested1><nested2>new text</nested2></elements></root>

I hope you can see and understand my problem. I am looking for a proper solution, any guidance would be wonderful.

To clarify the problem, using the current solution that I have, nested elements are not merged.