def use_to_mobjects(self, use_element):
    ref = use_element.getAttribute('xlink:href')[1:]
    if (ref not in self.ref_to_element):
        warnings.warn(('%s not recognized' % ref))
        return VGroup()
    return self.get_mobjects_from(self.ref_to_element[ref])
def use_to_mobjects(self, use_element):
    ref = use_element.getAttribute('xlink:href')[1:]
    if (ref not in self.ref_to_element):
        warnings.warn(('%s not recognized' % ref))
        return VGroup()
    return self.get_mobjects_from(self.ref_to_element[ref])