Hi,

I am not sure that what I'm seeing is a bug or the intended behaviour. In common.py, class Request, line 380:
self.headers = CaseInsensitiveDict(encode(headers or {}))
The headers are parsed into a CaseInsensitiveDict, which means self.headers['content-type'], self.headers['Content-Type'] and self.headers['cONteNt-tYpE'] will all return the same value BUT the keys of the dictionary are still the ones with which the items were defined.

Line 386, all the _params are set to None, with full lower case keys.

Then line 406
self._params.update(self.headers)
So if some _params were set in the headers they should update the values here. Problem is, the headers all have first-letter capitalization. So passing a token through header will lead to have

self._params
    {"token": None, "Token": token_value}

request.token
    None

Is this the intended behaviour ? I guess not.