docs: def process_pending_config_xref_nodes(app, doctree, fromdocname):
      """Process the ``pending_config_xref`` nodes during the ``doctree-resolved``
      event to insert links to the locations of ``lsst-config-topic`` directives.
  
      See also
      --------
      `config_ref_role`
      `ConfigTopicTargetDirective`
      `pending_config_xref`
      """
      logger = getLogger(__name__)
      env = app.builder.env
  
      for node in doctree.traverse(pending_config_xref):
          content = []
  
          # The source of the node is the content the authored entered in the
          # lsst-config role
          role_parts = split_role_content(node.rawsource)
          config_id = format_config_id(role_parts['ref'])
          if role_parts['display']:
              # user's custom display text
              display_text = role_parts['display']
          elif role_parts['last_component']:
              # just the name of the class
              display_text = role_parts['ref'].split('.')[-1]
          else:
              display_text = role_parts['ref']
          link_label = nodes.literal()
          link_label += nodes.Text(display_text, display_text)
  
          if hasattr(env, 'lsst_task_topics') and \
                  config_id in env.lsst_task_topics:
              # A config topic, marked up with the lsst-task directive is
              # available
              config_data = env.lsst_task_topics[config_id]
  
              ref_node = nodes.reference('', '')
              ref_node['refdocname'] = config_data['docname']
              ref_node['refuri'] = app.builder.get_relative_uri(
                  fromdocname, config_data['docname'])
              ref_node['refuri'] += '#' + config_data['target']['refid']
  
              ref_node += link_label
  
              content.append(ref_node)
  
          else:
              # Fallback if the config topic isn't known. Just print the
              # role's formatted content.
              content.append(link_label)
  
              message = 'lsst-config could not find a reference to %s'
              logger.warning(message, role_parts['ref'], location=node)
  
          # replacing the pending_config_xref node with this reference
          node.replace_self(content)