code: def fix_relative_url(self, publish_type, rel_url):
          
          if publish_type == 'post':
              return self.fix_post_relative_url(rel_url), False
          elif publish_type == 'page':
              return self.fix_page_relative_url(rel_url)
          else:
              raise ValueError(
                  'Publish type "{}" is not supported'.format(publish_type))
docs: Fix post or page relative url to a standard, uniform format.
  
          :param publish_type: publish type ('post' or 'page')
          :param rel_url: relative url to fix
          :return: tuple(fixed relative url or file path if exists else None,
                         file exists or not)
          :raise ValueError: unknown publish type