docs: def _inception_table_links(self, href_list):
          """
          Sometimes the EPA likes to nest their models and tables -- model within
          a model within a model -- so this internal method tries to clear all
          that up.
          """
          tables = set()
          for link in href_list:
              if not link.startswith('http://'):
                  link = self.agency_url + link
              html = urlopen(link).read()
              doc = lh.fromstring(html)
              area = doc.cssselect('map area')
              if area:
                  # Then this is a model containing models.
                  tables.update((a.attrib['href'] for a in area))
              else:
                  # The link is a table without additional models.
                  tables.update(link)
          return tables