code: def load_key(self, key):
          
  
          self._serialize(key)
          if isinstance(key, rsa.RSAPrivateKey):
              self.priv_key = key
              self.pub_key = key.public_key()
          else:
              self.pub_key = key
  
          return self
docs: Load a RSA key. Try to serialize the key before binding it to this
          instance.
  
          :param key: An RSA key instance