code: def set_scale(self, xscale=None, yscale=None, zscale=None, reset_camera=True):
          
          if xscale is None:
              xscale = self.scale[0]
          if yscale is None:
              yscale = self.scale[1]
          if zscale is None:
              zscale = self.scale[2]
          self.scale = [xscale, yscale, zscale]
  
          # Update the camera's coordinate system
          transform = vtk.vtkTransform()
          transform.Scale(xscale, yscale, zscale)
          self.camera.SetModelTransformMatrix(transform.GetMatrix())
          self.parent._render()
          if reset_camera:
              self.update_bounds_axes()
              self.reset_camera()
docs: Scale all the datasets in the scene.
          Scaling in performed independently on the X, Y and Z axis.
          A scale of zero is illegal and will be replaced with one.