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

def ChangeScaleFactor(self, newfactor):
    """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
    """
    if float(newfactor) > 0 and float(newfactor) < self._MAX_ZOOM:
      self._zoomfactor = newfactor