http://westside-consulting.blogspot.com/2019/10/certsession.html
This package provides an object, CertSession, based on requests.session that takes an alternate issuer certificate or issuer certificates collection as its single argument. Subsequent http requests made with this object will use both the given issuer certificate collection as well as the certificate collection provided by certifi.
pip install cert_session
from certsession import Session
session = Session('/path/to/my-root-certificates.pem')
response = session.get('https://my-web-service/...')
assert response.status_code == 200