def get_authentication_validation_session(self, proxy=None):
if proxy is None:<EOL><INDENT>raise NullArgument()<EOL><DEDENT>raise Unimplemented()<EOL>
Gets the ``OsidSession`` associated with the ``AuthenticationValidation`` service using the supplied ``Authentication``.

        arg:    proxy (osid.proxy.Proxy): a proxy
        return:
                (osid.authentication.process.AuthenticationValidationSes
                sion) - an ``AuthenticationValidationSession``
        raise:  NullArgument - ``proxy`` is ``null``
        raise:  OperationFailed - unable to complete request
        raise:  Unimplemented - ``supports_authentication_validation()``
                is ``false``
        *compliance: optional -- This method must be implemented if
        ``supports_validation()`` is ``true``.*