code: def get_access_token(self, oauth_token, oauth_token_secret, oauth_verifier):
          
          # Using OAuth1Session
          oauth = OAuth1Session(self.consumer_key,
                                client_secret=self.consumer_secret,
                                resource_owner_key=oauth_token,
                                resource_owner_secret=oauth_token_secret,
                                verifier=oauth_verifier)
          oauth_tokens = oauth.fetch_access_token(self.ACC_TOKEN)
  
          return oauth_tokens
docs: get the access token
              the url to go back after the external service call
              :param oauth_token: oauth token
              :param oauth_token_secret: oauth secret token
              :param oauth_verifier: oauth verifier
              :type oauth_token: string
              :type oauth_token_secret: string
              :type oauth_verifier: string
              :rtype: dict