Python: append multiple sub-elements to a parent element by reading from a string

Question

I am new to python and trying to read and add multiple xml elements represented by a string as a subelement of an XML element.

For eg:

<student>
        <name>abc</name>
        <description>abcd</description>     
        <regno>200</regno>
</student>

I have a string which can represent further student info which may contain nested information as well. For eg:

"<grade>100</grade><address-info><street>xyz</street><city>efgh</city><zip>505050</zip></address-info>"

I need this string to be parsed and to be added inside the student element and result in something like

<student>
    <name>abc</name>
    <description>abcd</description>     
    <regno>200</regno>
    <grade>100</grade>
    <address-info>
         <street>xyz</street>
         <city>efgh</city>
         <zip>505050</zip>
     </address-info>
</student>

I tried using append method which is resulting in an error

def add_cfg_under_correct_student(in_name, cfg_to_be_added, root):
    if root is None:
        return True
    for student in root.findall('student'):
        name = student.find('name')
        if name.text != in_name:
            continue
        student.append(ET.fromstring(cfg_to_be_added))
    return True

But I got an error as Traceback (most recent call last): add_cfg_under_correct_student student.append(ET.fromstring(cfg_to_be_added))

File "src/lxml/lxml.etree.pyx", line 3213, in lxml.etree.fromstring (src/lxml/lxml.etree.c:79003)

File "src/lxml/parser.pxi", line 1848, in lxml.etree._parseMemoryDocument (src/lxml/lxml.etree.c:118334)

File "src/lxml/parser.pxi", line 1736, in lxml.etree._parseDoc (src/lxml/lxml.etree.c:117014)

File "src/lxml/parser.pxi", line 1102, in lxml.etree._BaseParser._parseDoc (src/lxml/lxml.etree.c:111258)

File "src/lxml/parser.pxi", line 595, in lxml.etree._ParserContext._handleParseResultDoc (src/lxml/lxml.etree.c:105102)

File "src/lxml/parser.pxi", line 706, in lxml.etree._handleParseResult (src/lxml/lxml.etree.c:106810)

File "src/lxml/parser.pxi", line 635, in lxml.etree._raiseParseError (src/lxml/lxml.etree.c:105664) File "", line 1

lxml.etree.XMLSyntaxError: Extra content at the end of the document, line 1, column 27

Then I tried using the ET.ElementTree(ET.fromstring(xmlstring)) option as suggested in this answer, but still get a similar error.

Then I looked up another answer on adding multiple elements at once in this question, but it doesn't exactly solve my scenario.

Does the solution mentioned in the above question to use extend work on sub elements which in turn could have sub elements under them as well?

Please help