code: def delete_link(self, rel=None, href=lambda _: True):
          
          if not LINKS_KEY in self.o:
              return
  
          links = self.o[LINKS_KEY]
          if rel is None:
              for rel in list(links.keys()):
                  self.delete_link(rel, href)
              return
  
          if callable(href):
              href_filter = href
          else:
              href_filter = lambda x: x == href
  
          links_for_rel = links.setdefault(rel, [])
          if isinstance(links_for_rel, dict):
              links_for_rel = [links_for_rel]
  
          new_links_for_rel = []
          for link in links_for_rel:
              if not href_filter(link['href']):
                  new_links_for_rel.append(link)
  
          if new_links_for_rel:
              if len(new_links_for_rel) == 1:
                  new_links_for_rel = new_links_for_rel[0]
  
              links[rel] = new_links_for_rel
          else:
              del links[rel]
  
          if not self.o[LINKS_KEY]:
              del self.o[LINKS_KEY]
docs: Deletes links from the document.
  
          Calling code should use this method to remove links instead of
          modyfying ``links`` directly.
  
          The optional arguments, ``rel`` and ``href`` are used to select the
          links that will be deleted. If neither of the optional arguments are
          given, this method deletes every link in the document. If ``rel`` is
          given, only links for the matching link relationship type are deleted.
          If ``href`` is given, only links with a matching ``href`` are deleted.
          If both ``rel`` and ``href`` are given, only links with matching
          ``href`` for the matching link relationship type are delted.
  
          Arguments:
  
          - ``rel``: an optional string specifying the link relationship type of
                     the links to be deleted.
          - ``href``: optionally, a string specifying the ``href`` of the links
                      to be deleted, or a callable that returns true when its
                      single argument is in the set of ``href``s to be deleted.