lxml error on elevation

[BartPigula]

While trying to elevate a chosen xml file i got an error:

stix2_elevator '/home/b.pigula/cti-ai/data/cisa-xml-files/analysis-reports/aa23-074a.stix__0.xml'
[stixmarx.utils] [WARNING] [2025-09-17 10:41:26,455] No module named 'stix.report'
Results produced by the stix2-elevator are not for production purposes.
Traceback (most recent call last):
  File "/home/b.pigula/cti-ai/cti-env/bin/stix2_elevator", line 8, in <module>
    sys.exit(main())
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stix2elevator/cli.py", line 221, in main
    result = elevate(elevator_args.file_)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stix2elevator/__init__.py", line 103, in elevate
    container = stixmarx.parse(stix_package)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/__init__.py", line 26, in parse
    stix_package = parser.parse_xml(xml_input, encoding)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/parser.py", line 294, in parse_xml
    parser = MarkingParser(root=xml_input, encoding=encoding)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/parser.py", line 79, in __init__
    self._markingmap = markingmap.build(self._root, encoding)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/markingmap.py", line 237, in build
    marked.addall(nodeset, spec)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/markingmap.py", line 157, in addall
    self.add(key, value)
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/markingmap.py", line 139, in add
    key = self._make_key(key)  # Reduce the amount of casting
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/markingmap.py", line 120, in _make_key
    elif xml.is_content(node):
  File "/home/b.pigula/cti-ai/cti-env/lib/python3.10/site-packages/stixmarx/xml.py", line 59, in is_content
    return ((isinstance(node, etree._ElementStringResult) or
AttributeError: module 'lxml.etree' has no attribute '_ElementStringResult'. Did you mean: '_ElementUnicodeResult'?

I am using stix2-elevator version 4.1.7 and lxml version 6.0.1. Steps to reproduce the issue are to install those libraries and try to convert any xml file :)
What i've found is that after downgrading lxml to 4.9.3 the conversion runs fine - so i guess the version of lxml should be forced on installation of stix2-elevator