docs: def explicit_rel_links(self, rels=('homepage', 'download')):
          """Yields all links with the given relations"""
          for match in self._rel_re.finditer(self.content):
              found_rels = match.group(1).lower().split()
              for rel in rels:
                  if rel in found_rels:
                      break
              else:
                  continue
              match = self._href_re.search(match.group(0))
              if not match:
                  continue
              url = match.group(1) or match.group(2) or match.group(3)
              url = self.clean_link(urlparse.urljoin(self.base_url, url))
              yield Link(url, self)