Hi , I noticed that getheaders() is used when working with urllib3.response.HTTPResponse. This method is deprecated in urllib3 and raises a DepricationWarning error. Maybe it worth considering using headers property
https://github.com/HubSpot/hubspot-api-python/blame/d1eff4b5846f8a4c7cdbc96a2c72930b8d96bb80/hubspot/marketing/transactional/rest.py#L41