code: def is_valid_api_key(self):
          
          res = self.send('api/v3/api_keys', 'get')
          return \
              res.ok and \
              self.api_key in (ak['token'] for ak in res.json()['result'])
docs: Checks validity. Right now, an API key is considered valid if it
          can list user API keys and the result contains that API key.
          This might change in the future.
  
          :return: True if the API key is considered valid for current user.