def save_wavefront(self, file_name):
        if len(file_name) != 0:
            ex = tvtk.OBJExporter()
            self._lift()
            ex.input = self._renwin
            f_pref = os.path.splitext(file_name)[0]
            ex.file_prefix = f_pref
            self._exporter_write(ex)
Return the appropriate key code for the units value for the axes by
dataset/ETHPy150Open enthought/mayavi/tvtk/pyface/tvtk_scene.py/TVTKScene.save_wavefront--crossover with--dataset/ETHPy150Open ejeschke/ginga/ginga/util/wcsmod.py/choose_coord_units