Ensure the root element is a supported version.

        Args:
            root (etree.Element)

        Raises:
            UnsupportedVersionError

def _check_version(self, root):
        """Ensure the root element is a supported version.

        Args:
            root (etree.Element)

        Raises:
            UnsupportedVersionError
        """
        version = self._get_version(root)
        supported = [StrictVersion(x) for x in
                     self.supported_versions(root.tag)]

        if version in supported:
            return

        error = "Document version ({0}) not in supported versions ({1})"
        raise UnsupportedVersionError(
            message=error.format(version, supported),
            expected=supported,
            found=version
        )