XML : ElementTree Returns Element Instead of ElementTree

I am trying to build an ElementTree from a string. When I do the following (as set out in Python ElementTree: Parsing a string and getting ElementTree instance), I get an Element instead of an ElementTree:

  companyTree = ElementTree.ElementTree(ElementTree.fromstring('<companies></companies>'))    

If I do

  print(root.getroot())    

I get

AttributeError: 'xml.etree.ElementTree.Element' object has no attribute 'getroot'

In other words, companyTree is an Element instead of an ElementTree. According to the accepted answer in 1, I should be getting an ElementTree. Has the API changed? How do I get an ElementTree from a string now? Thanks.

Note that there is more on this problem in Python ElementTree: ElementTree vs root Element