def _unregister(self, cls):
        """Unregisters the given class.

        If the specified class isn't registered, ``NotRegistered`` will
        be raised.
        """
        if not issubclass(cls, self._registerable_class):
            raise ValueError('Only %s classes or subclasses may be '
                             'unregistered.' % self._registerable_class)

        if self._registry.keys() not in cls:
            raise NotRegistered('%s is not registered' % cls)

        del self._registry[cls]

        return True
dataset/ETHPy150Open Havate/havate-openstack/proto-build/gui/horizon/Horizon_GUI/horizon/base.py/Registry._unregister/swapped operands of `not in`