Renders the HTML representation of the element.

def render(self, **kwargs):
        """Renders the HTML representation of the element."""
        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)