Unable to get access token for lyft api - access-token

Question

I am trying to use the lyft developer api. I created a new app to get the client Id and client secret . I am following the steps in https://developer.lyft.com/docs/authentication to get an access token in my python code. But I always get the error, "unauthorized client". Can anyone point out my mistake?
def __init__(self):
self.client_id = 'MY_ID'
self.client_secret = 'MY_SECRET'
# obtain access token
self.token = self.__generate_token__()
# define variables to be used in the request parameters
token_val = 'Bearer '+self.token
self.headers = {'Authorization':token_val}
def __generate_token__(self):
url = 'https://api.lyft.com/oauth/token'
# define request parameters
payload = {"Content-Type": "application/json",
"grant_type": "client_credentials",
"scope": "public"}
# request data
res = requests.post(url,
data = payload,
auth = (self.client_id, self.client_secret))
# extract the token from the response
token = res.json()['access_token']
return token

Answer 1

This is a working example for a Java client
https://github.com/yschimke/oksocial/blob/175bdbf66e312d8bdf79183a140c2c5270329cf2/src/main/java/com/baulsupp/oksocial/services/lyft/LyftClientAuthFlow.java
The main thing that looks wrong, is sending "Content-Type" in the POST data body instead of as a header indicating the format of the data.
It looks like from the requests api that you should be sending "json = payload" instead of "data". But I'm not an expert on this python API.
The curl equivalent of the above java code also works
$ ./oksocial --curl --authorize lyft --client
Authorising Lyft API
Lyft Client Id [***********]:
Lyft Client Secret [********************************]:
curl -X POST -H "Authorization:Basic ******************" -H "Connection:Keep-Alive" -H "User-Agent:okhttp/3.5.0" -H "Host:api.lyft.com" -H "Accept-Encoding:gzip" -H "Content-Length:55" -H "Content-Type:application/json; charset=utf-8" -H "Content-Type:application/json; charset=utf-8" -d '{"grant_type": "client_credentials", "scope": "public"}' https://api.lyft.com/oauth/token