code: def __prepare_token_request(self, params, url=None):
          
          if self.secret_key is None:
              params['code_verifier'] = self.code_verifier
              params['client_id'] = self.client_id
  
          request_params = {
              'headers': self.__get_basic_auth_header(),
              'data': params,
              'url': self.oauth_token if url is None else url,
          }
  
          return request_params
docs: Generate the request parameters to execute the POST call to
          get or refresh a token.
  
          Parameters
          ----------
          params : dictionary
              Contains the parameters that will be given as data to the oauth
              endpoint
  
          Returns
          -------
          type
              The filled request parameters with all required informations