code: def render(self, **kwargs):
          
          if isinstance(self._parent, GeoJson):
              keys = tuple(self._parent.data['features'][0]['properties'].keys())
              self.warn_for_geometry_collections()
          elif isinstance(self._parent, TopoJson):
              obj_name = self._parent.object_path.split('.')[-1]
              keys = tuple(self._parent.data['objects'][obj_name][
                               'geometries'][0]['properties'].keys())
          else:
              raise TypeError('You cannot add a GeoJsonTooltip to anything else '
                              'than a GeoJson or TopoJson object.')
          keys = tuple(x for x in keys if x not in ('style', 'highlight'))
          for value in self.fields:
              assert value in keys, ('The field {} is not available in the data. '
                                     'Choose from: {}.'.format(value, keys))
          super(GeoJsonTooltip, self).render(**kwargs)
docs: Renders the HTML representation of the element.