docs: def on_callback(self,auth_resp):
          """ Must be called once the authorisation server has responded after
              redirecting to the url provided by 'get_authorisation_url' and completing
              the login there.
              Returns True if a token was successfully retrieved, False otherwise."""
          try:
              oauth = OAuth2Session(self.client_id,state=self.state,redirect_uri=self.redirect_url)
              self.token = oauth.fetch_token(self.token_url,
                                             authorization_response=auth_resp,
                                             client_secret=self.client_secret,
                                             verify=self.verifySSL)
              if not self.api_key and self.API_KEY_DEFAULT:
                  self.get_api_key()
                  if not self.api_key:
                      self.API_KEY_DEFAULT = False
          except Exception:
              #print("Unexpected error:", sys.exc_info()[0])
              #print("Could not fetch token from OAuth Callback!")
              return False
          return True