Is there any function which can search for duplicate node based on specific attribute value and copy sub-elements/child elements to it?

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XML

Python3.6

Hi, I have started learning programming for my research purpose. I am having bit of trouble working with XML files since I an new to it. Well my question is, How to match an attribute value of node element and update duplicate node with sub-element in XML file?

Input XML file:

    <brand by="rtrtrtrt" date="2014/01/01" name="OOP-112200" insti="TGA">
    <exp name="OOP-112200" own="TGA" descri="" sound_db="JJKO">
    <elem name="abcd" sound_freq="abcd" c_ty="pv">
    <feature number="48">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="abcd" first_name="g7tty" description="xyz">
    
    <elem tension="SGCGGSCGSC" name="M_20_K40745170" sound_freq="mhr17:7907527-7907589" s_c="0">
    <feature number="5748">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">
    <act db="Acc" value="PM_1234555|ta">
    <act db="pval" value="0.1">
    <act db="xyz" value="abc">
    <per fre="Volum_5mb" value="89.00">
    <per fre="Volum_40mb" value="44.00">
    <per fre="Volum_70mb" value="77.00">
    
    
    <elem tension="SGCGSCGSCGSCGSC" name="M_20_K40745172" sound_freq="mhr17:7907527-7907100" 
="" s_c="0">
    <feature number="5748">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">
    <act db="Acc" value="PR_0987677|wa">
    <act db="pval" value="0.99">
    <act db="xyz" value="abc">
    <per fre="Volum_5mb" value="99.00">
	<per fre="Volum_40mb" value="57.00">
    <per fre="Volum_70mb" value="88.00">
    
    
    <elem tension="SGCGSCGSCGSCGSC" name="M_20_K40745172" sound_freq="mhr17:7907527-7907100" 
="" s_c="0">
    <feature number="57477">
    <tfgt v="0.1466469683747654" y="0.39999" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">

I want to find duplicate node by matching element elem name value in file and update duplicate node with sub-element in XML file. (for example duplicate in this set 'M_20_K40745172')

I am expecting :

    <brand by="hhdhdh" date="2014/01/01" name="OOP-112200" insti="TGA">
    <exp name="OOP-112200" own="TGA" descri="" sound_db="JJKO">
    <elem name="abcd" sound_freq="abcd" c_ty="pv">
    <feature number="48">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="abcd" first_name="g7tty" description="xyz">
    
    <elem tension="SGCGGSCGSC" name="M_20_K40745170" sound_freq="mhr17:7907527-7907589" s_c="0">
    <feature number="5748">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">
    <act db="Acc" value="PM_1234555|ta">
    <act db="pval" value="0.1">
    <act db="xyz" value="abc">
    <per fre="Volum_5mb" value="89.00">
    <per fre="Volum_40mb" value="44.00">
    <per fre="Volum_70mb" value="77.00">
    
    
    <elem tension="SGCGSCGSCGSCGSC" name="M_20_K40745172" sound_freq="mhr17:7907527-7907100" 
="" s_c="0">
    <feature number="5748">
    <tfgt v="0.1466469683747654" y="0.0" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">
    <act db="Acc" value="PR_0987677|wa">
    <act db="pval" value="0.99">
    <act db="xyz" value="abc">
    <per fre="Volum_5mb" value="99.00">
	<per fre="Volum_40mb" value="57.00">
    <per fre="Volum_70mb" value="88.00">
    
    
    <elem tension="SGCGSCGSCGSCGSC" name="M_20_K40745172" sound_freq="mhr17:7907527-7907100" 
="" s_c="0">
    <feature number="57477">
    <tfgt v="0.1466469683747654" y="0.39999" units="elem">    
    <swan sound_freq="mhr17:7907527-7907589" first_name="g7tty" description="xyz">
    <act db="Acc" value="PR_0987677|wa">
    <act db="pval" value="0.99">
    <act db="xyz" value="abc">
    <per fre="Volum_5mb" value="99.00">
	<per fre="Volum_40mb" value="57.00">
    <per fre="Volum_70mb" value="88.00">

Any help would be appreciated. Thanks in advance!

What I have tried:

Right now I am studying XML parsing module like etree to solve this

I use pandas data frame to modify XML earlier, but not able to modify duplicates. I dont want to ingore duplicates.

df:

             id	          pval	       Acc
    1  M_20_K40745170	   0.1	      PM_1234555|ta
    2  M_20_K40745172	   0.99	      PR_0987677|wa

Here's my script :

import xml.etree.ElementTree as et

tree = et.parse('input_xml.xml')
root = tree.getroot()

for index, row in df.iterrows():
    node = root.find('./brand/sec[@name="{}"]//mwan'.format(row['id']))
    print(node)

    for name in ['acc','pval']:
        item = node.find('./per[@name="{}"]'.format(name))

        if not item:
            item = et.SubElement(node, 'per')
            item.tail = '\n'
            item.set('fre', name)
            item.tail = '\n'
            item.set('value', (row[name]))

tree.write('out.xml')