@classmethod
def _determine_region_id(cls, element):
    """Determines the TT region of an element.

        For determining the region of an element, check out the url, look for
        section "[associate region]". One difference, is that we leave the
        default region id empty. The writer will know what to do:
        http://www.w3.org/TR/ttaf1-dfxp/#semantics-region-layout-step-1

        :param element: the xml element for which we're trying to get region
            info
        """
    region_id = None
    if hasattr(element, u'get'):
        region_id = element.get(u'region')
    if not region_id:
        region_id = cls._get_region_from_ancestors(element)
    if not region_id:
        try:
            region_id = cls._get_region_from_descendants(element)
        except LookupError:
            return
    return region_id
