说明和 Model
环境：
➜ python
Python 3.6.3 |Anaconda custom (x86_64)| (default, Oct 6 2017, 12:04:38)
[GCC 4.2.1 Compatible Clang 4.0.1 (tags/RELEASE_401/final)] on darwin
Type help, copyright, credits or license for more information.
>>> import django
>>> print(django.get_version())
2.0.1
>>>
20
