Generate GPX element tree from ``Waypoints`` object.

        Returns:
            etree.ElementTree: GPX element tree depicting ``Waypoints`` object

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

        Returns:
            etree.ElementTree: GPX element tree depicting ``Waypoints`` object
        """
        gpx = create_elem('gpx', GPX_ELEM_ATTRIB)
        if not self.metadata.bounds:
            self.metadata.bounds = self[:]
        gpx.append(self.metadata.togpx())
        for place in self:
            gpx.append(place.togpx())

        return etree.ElementTree(gpx)