def tostr(dt):
    date = iso8601.parse(dt)
    return iso8601.tostring(date)
 def test_tostring(self):
     dt = iso8601.parse('1998-06-13T14:12Z')
     self.assertEqual(iso8601.tostring(dt), '1998-06-13T14:12Z')
     self.assertEqual(iso8601.tostring(dt, 'Z'), '1998-06-13T14:12Z')
     self.assertEqual(iso8601.tostring(dt, '-05:00'), '1998-06-13T09:12-05:00')