code: def setZoomAmount(self, amount):
          
          amount = max(self._minZoomAmount, amount)
          amount = min(self._maxZoomAmount, amount)
          
          # only update when necessary
          if amount == self.zoomAmount():
              return
          
          # calculate the scalar value
          scale = (amount / 100.0)
          
          # assign the new transform to all of the views
          view = self.mainView()
          view.setTransform(QTransform.fromScale(scale, scale))
          
          # emit the value changed signal for the scene
          if not (self.signalsBlocked() or view.signalsBlocked()):
              view.zoomAmountChanged.emit(amount)
docs: Sets the zoom level for the current scene, updating all the \
          views that it is connected to.
          
          :param      amount      <int>  (100 based %)