def get_expiration(self):
if not self.has_expiration():<EOL><INDENT>raise errors.IllegalState()<EOL><DEDENT>else:<EOL><INDENT>raise errors.Unimplemented()<EOL><DEDENT>
Gets the expiration date associated with this authentication credential.

        Consumers should check for the existence of a an expiration
        mechanism via ``hasExpiration()``.

        return: (timestamp) - the expiration date of this authentication
                credential
        raise:  IllegalState - ``has_expiration()`` is ``false``
        *compliance: mandatory -- This method must be implemented.*