code: def auth_string(self):
          '''
          Authenticate based on username and token which is base64-encoded
          '''
  
          username_token = '{username}:{token}'.format(username=self.username, token=self.token)
          b64encoded_string = b64encode(username_token)
          auth_string = 'Token {b64}'.format(b64=b64encoded_string)
  
          return auth_strinf auth_string(self):
          '''
          Authenticate based on username and token which is base64-encoded
          '''
  
          username_token = '{username}:{token}'.format(username=self.username, token=self.token)
          b64encoded_string = b64encode(username_token)
          auth_string = 'Token {b64}'.format(b64=b64encoded_string)
  
          return auth_string
docs: Authenticate based on username and token which is base64-encoded