'Dummy client used when an invalid client key is supplied.
The dummy client should be associated with either a client secret,
a rsa key or both depending on which signature methods are supported.
Providers should make sure that
get_client_secret(dummy_client)
get_rsa_key(dummy_client)
return a valid secret or key for the dummy client.'

@property
def dummy_client(self):

    raise NotImplementedError('Subclasses    must    implement    this    function.')
