[lxml] Canonicalization of PROV-XML Documents fails

Hey everyone, i want to canonicalize Prov Documents, which are encoded according to the PROV-XML Scheme (https://www.w3.org/TR/prov-xml/). I used the etree.canonicalize method with the following XML document: https://openprovenance.org/store/documents/5763.xml . Unfortunately the order of elements remains unchanged. I tried to pass the XML via file and via string - but the cancolized document look unchanged. Does lxml cant deal with XML-Extensions?