code: def ghuser_role(name, rawtext, text, lineno, inliner, options={}, content=[]):
      
      app = inliner.document.settings.env.app
      #app.info('user link %r' % text)
      ref = 'https://www.github.com/' + text
      node = nodes.reference(rawtext, text, refuri=ref, **options)
      return [node], []
docs: Link to a GitHub user.
  
      Returns 2 part tuple containing list of nodes to insert into the
      document and a list of system messages.  Both are allowed to be
      empty.
  
      :param name: The role name used in the document.
      :param rawtext: The entire markup snippet, with role.
      :param text: The text marked with the role.
      :param lineno: The line number where rawtext appears in the input.
      :param inliner: The inliner instance that called us.
      :param options: Directive options for customization.
      :param content: The directive content for customization.