docs: def sign(self, payload, signing_key_or_keys):
          """
          Create a JWT with one or more keys.
          Returns a compact-form serialized JWT if there is only one key to sign with
          Returns a JSON-structured serialized JWT if there are multiple keys to sign with
          """
          if isinstance(signing_key_or_keys, list):
              return self._sign_multi(payload, signing_key_or_keys)
  
          else:
              return self._sign_single(payload, signing_key_or_keys)