code: def add_link(self, rel, target, wrap=False, **kwargs):
          
          if isinstance(target, bytes):
              target = target.decode('utf-8')
          if isinstance(target, str) or isinstance(target, unicode):
              new_link = dict(href=target, **kwargs)
          else:
              new_link = dict(href=target.url(), **kwargs)
  
          self._add_rel('_links', rel, new_link, wrap)
          return self
docs: Adds a link to the document.
  
          This method adds a link to the given ``target`` to the document with
          the given ``rel``. If one or more links are already present for that
          link relationship type, the new link will be added to the existing
          links for that link relationship type.
  
          Unlike ``dougrain.Document.add_link``, this method does not detect
          equivalence between relationship types with different representations.
  
          If ``target`` is a string, a link is added with ``target`` as its
          ``href`` property and other properties from the keyword arguments.
  
          If ``target`` is a ``dougrain.Document`` object, a link is added with
          ``target``'s URL as its ``href`` property and other property from the
          keyword arguments.
  
          If ``target`` is a ``Builder`` object, a link is added with
          ``target``'s URL as its ``href`` property and other property from the
          keyword arguments.
  
          This method returns self, allowing it to be chained with additional
          method calls.
  
          Arguments:
  
          - ``rel``: a string specifying the link relationship type of the link.
            It should be a well-known link relation name from the IANA registry
            (http://www.iana.org/assignments/link-relations/link-relations.xml),
            a full URI, or a CURIE.
          - ``target``: the destination of the link.
          - ``wrap``: Defaults to False, but if True, specifies that the link
            object should be initally wrapped in a JSON array even if it is the
            first link for the given ``rel``.