code: def _load_panel_customization(self):
          
          panel_customization = self._conf.get("panel_customization", [])
  
          # Process all the panel groups first so that they exist before panels
          # are added to them and Dashboard._autodiscover() doesn't wipe out any
          # panels previously added when its panel groups are instantiated.
          panel_configs = []
          for config in panel_customization:
              if config.get('PANEL'):
                  panel_configs.append(config)
              elif config.get('PANEL_GROUP'):
                  self._process_panel_group_configuration(config)
              else:
                  LOG.warning("Skipping %s because it doesn't have PANEL or "
                              "PANEL_GROUP defined.", config.__name__)
          # Now process the panels.
          for config in panel_configs:
              self._process_panel_configuration(config)
docs: Applies the plugin-based panel configurations.
  
          This method parses the panel customization from the ``HORIZON_CONFIG``
          and make changes to the dashboard accordingly.
  
          It supports adding, removing and setting default panels on the
          dashboard. It also support registering a panel group.