code: def create_claims_set(self, request, userid, extra_claims=None):
          
          claims_set = {self.userid_claim: userid}
          now = timegm(datetime.utcnow().utctimetuple())
          if self.expiration_delta is not None:
              claims_set['exp'] = now + self.expiration_delta
          if self.issuer is not None:
              claims_set['iss'] = self.issuer
          if self.allow_refresh:
              if self.refresh_delta is not None:
                  claims_set['refresh_until'] = now + self.refresh_delta
              if self.refresh_nonce_handler is not None:
                  claims_set['nonce'] = self.refresh_nonce_handler(request,
                                                                   userid)
          if extra_claims is not None:
              claims_set.update(extra_claims)
          return claims_set
docs: Create the claims set based on the userid of the claimed identity,
          the settings and the extra_claims dictionary.
  
          The userid will be stored in settings.jwtauth.userid_claim
          (default: "sub").
          If settings.jwtauth.expiration_delta is set it will be added
          to the current time and stored in the "exp" claim.
          If settings.jwtauth.issuer is set, it get stored in the "iss" claim.
          If settings.jwtauth.refresh_delta is set it will be added
          to the current time and stored in the "refresh_until" claim and
          the return value of settings.jwtauth.refresh_nonce_handler called with
          "user_id" as argument will be stored in the "nonce" claim.
  
          With the extra_claims dictionary you can provide additional claims.
          This can be registered claims like "nbf"
          (the time before which the token should not be processed) and/or
          claims containing extra info
          about the identity, which will be stored in the Identity object.
  
          :param request: current request object.
          :type request: :class:`morepath.Request`
          :param userid:  the userid of the claimed identity.
          :param extra_claims: dictionary, containing additional claims or None.