code: def add_link(self, rel, value, href=None):
          
          links_node = self.metadata.find('links')
          if links_node is None:
              links_node = ioc_et.make_links_node()
              self.metadata.append(links_node)
          link_node = ioc_et.make_link_node(rel, value, href)
          links_node.append(link_node)
          return True
docs: Add a Link metadata element to the IOC.
  
          :param rel: Type of the link.
          :param value: Value of the link text.
          :param href: A href value assigned to the link.
          :return: True