docs: def _request_access_token(self):
          """Gets client credentials access token """
          payload = {'grant_type': 'authorization_code',
                     'code': code,
                     'redirect_uri': self.redirect_uri}
  
          headers = _make_authorization_headers(self.client_id,
                                                self.client_secret)
  
          response = requests.post(self.OAUTH_TOKEN_URL, data=payload,
                                   headers=headers,
                                   verify=LOGIN_VERIFY_SSL_CERT)
  
          if response.status_code is not 200:
              raise MercedesMeAuthError(response.reason)
          token_info = response.json()
          return token_info