code: def _get_version(self, root):
          
          # Note: STIX and MAEC use a "version" attribute. To support CybOX, a
          # subclass will need to combine "cybox_major_version",
          # "cybox_minor_version", and "cybox_update_version".
          version = self.get_version(root)
          if version:
              return StrictVersion(version)
  
          raise UnknownVersionError(
              "Unable to determine the version of the input document. No "
              "version information found on the root element."
          )
docs: Return the version of the root element passed in.
  
          Args:
              root (etree.Element)
  
          Returns:
              distutils.StrictVersion
  
          Raises:
              UnknownVersionError