def METHOD_NAME(self, delta):
    _delta = abs(delta / 1000)
    if delta > 0:
        self.magnification += _delta
    else:
        self.magnification -= _delta
    if self.magnification > self._max_magnification:
        self.magnification = self._max_magnification
    elif self.magnification < self._min_magnification:
        self.magnification = self._min_magnification