code: def _verify_required_claims_exist(jwt_claims):
      
      for claim_name in [u"aud", u"exp", u"iss", u"sub"]:
          if claim_name not in jwt_claims:
              raise suppliers.UnauthenticatedException(u'Missing "%s" claim' % claim_name)
docs: Verifies that the required claims exist.
  
      Args:
        jwt_claims: the JWT claims to be verified.
  
      Raises:
        UnauthenticatedException: if some claim doesn't exist.