code: def generic_ref_formatter(view, context, model, name, lazy=False):
      
      try:
          if lazy:
              rel_model = getattr(model, name).fetch()
          else:
              rel_model = getattr(model, name)
      except (mongoengine.DoesNotExist, AttributeError) as e:
          # custom_field_type_formatters seems to fix the issue of stale references
          # crashing pages, since it intercepts the display of all ReferenceField's.
          return Markup(
              '<span class="label label-danger">Error</span> <small>%s</small>' % e
          )
  
      if rel_model is None:
          return ''
  
      try:
          return Markup(
              '<a href="%s">%s</a>'
              % (
                  url_for(
                      # Flask-Admin creates URL's namespaced w/ model class name, lowercase.
                      '%s.details_view' % rel_model.__class__.__name__.lower(),
                      id=rel_model.id,
                  ),
                  rel_model,
              )
          )
      except werkzeug.routing.BuildError as e:
          return Markup(
              '<span class="label label-danger">Error</span> <small>%s</small>' % e
          )
docs: For GenericReferenceField and LazyGenericReferenceField
  
      See Also
      --------
      diff_formatter