Generate GPX element tree from ``Trackpoints``.

        Returns:
            etree.ElementTree: GPX element tree depicting ``Trackpoints``
                objects

def export_gpx_file(self):
        """Generate GPX element tree from ``Trackpoints``.

        Returns:
            etree.ElementTree: GPX element tree depicting ``Trackpoints``
                objects
        """
        gpx = create_elem('gpx', GPX_ELEM_ATTRIB)
        if not self.metadata.bounds:
            self.metadata.bounds = [j for i in self for j in i]
        gpx.append(self.metadata.togpx())
        track = create_elem('trk')
        gpx.append(track)
        for segment in self:
            chunk = create_elem('trkseg')
            track.append(chunk)
            for place in segment:
                chunk.append(place.togpx())

        return etree.ElementTree(gpx)