Comment 1 for bug 1342469

It actually says

"""
        Creates an iterator for the root element. The iterator loops over
        all elements in this tree, in document order.
"""

Note the "root element" bit. I've added a comment to make it clearer:

https://github.com/lxml/lxml/commit/44ec7b535d1a342b3c4b6070ebd2a4c3e29595f7