code: def ChangeScaleFactor(self, newfactor):
      
      if float(newfactor) > 0 and float(newfactor) < self._MAX_ZOOM:
        self._zoomfactor = newfactor
docs: Changes the zoom of the graph manually.
  
      1.0 is the original canvas size.
  
      Args:
        # float value between 0.0 and 5.0
        newfactor: 0.7