Am trying to access the below API to get access token but am getting error mentioned below the code snippet: from requests.auth import HTTPBasicAuth from oauthlib.oauth2 import BackendApplicationClient from requests_oauthlib import OAuth2Session auth_token_url = "https://authz.constantcontact.com/oauth2/default/v1/token" client = BackendApplicationClient(client_id=client_id) oauth = OAuth2Session(client=client) basic_auth = HTTPBasicAuth(client_id, client_secret) token = oauth.fetch_token(token_url=auth_token_url, auth=basic_auth) What am i missing here? I need to get access token to make api call to below url:   https://api.cc.email/v3/contacts?include_count=true   Is there a way to generate access token that doesn't expire as am trying to build a data pipeline using this API call.    Error: UnauthorizedClientError: (unauthorized_client) The client is not authorized to use the provided grant type. Configured grant types: [authorization_code, implicit, refresh_token]. ... View more