Python文档说here“要构建具有非本地字节顺序的结构，您可以使用BigEndianStructure，LittleEndianStructure，BigEndianUnion和LittleEndianUnion基类之一”
然而：
Python 3.6.1 (default, Jul 13 2017, 21:35:51)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-11)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from ctypes import *
>>> BigEndianStructure
<class 'ctypes._endian.BigEndianStructure'>
>>> BigEndianUnion
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'BigEndianUnion' is not defined
任何人都知道如何使BigEndianUnion可用（理想情况下也使用python 2.7）？
提前致谢
[更新] p.s.打开https://bugs.python.org/issue33178