For a DITA document that contains a single language, the highest level element (i.e. map, concept, task, etc.) that contains content should set the @xml:lang attribute to the language that applies to the document.
The question: How do I set the @xml:lang attribute using lxml? Everyone seems confused on the forums.
The answer: It’s a special case.
from lxml import etree
tree = etree.parse('<map><topicref href="someFile"/><topicref href="otherFile"/></map>')
root = tree.getroot()
attr = root.attrib
attr['{http://www.w3.org/XML/1998/namespace}lang'] = "en-us"
That’s it. Once you know the trick, it’s fairly easy to script for your translation needs.
Spread the word.