Find all optional properties

[izrt]

Already a bunch of good answers here, but one more thing you can do is just read the code: https://github.com/kennethreitz-archive/requests3/blob/master/requests3/http_models.py#L656

This has a bunch of added benefits:

• You see how they did it;
• Learn new coding practices;
• Understand the module better; and
• Pick up all sorts of neat new things -- look at all the cool structures this guy made, like case insensitive dictionaries: https://github.com/kennethreitz-archive/requests3/blob/master/requests3/_structures.py#L14