code: def _make_jwt(self):
          
          now = _helpers.utcnow()
          lifetime = datetime.timedelta(seconds=self._token_lifetime)
          expiry = now + lifetime
  
          payload = {
              'iss': self._issuer,
              'sub': self._subject,
              'iat': _helpers.datetime_to_secs(now),
              'exp': _helpers.datetime_to_secs(expiry),
              'aud': self._audience,
          }
  
          payload.update(self._additional_claims)
  
          jwt = encode(self._signer, payload)
  
          return jwt, expiry
docs: Make a signed JWT.
  
          Returns:
              Tuple[bytes, datetime]: The encoded JWT and the expiration.