code: def test_points_sizes_scalar_update(self):
      hmap = HoloMap(
          {i: Points([1, 2, 3]).opts(s=i * 10) for i in range(1, 3)}
      )
      plot = mpl_renderer.get_plot(hmap)
      artist = plot.handles["artist"]
      plot.update((1,))
      self.assertEqual(artist.get_sizes(), np.array([10]))
      plot.update((2,))
      self.assertEqual(artist.get_sizes(), np.array([20]))
  
imports: import matplotlib.pyplot
  import numpy
  import pytest
  from holoviews.core.options import AbbreviatedException
  from holoviews.core.overlay import NdOverlay
  from holoviews.core.spaces import HoloMap
  from holoviews.element import Points
  from ..utils import ParamLogStream
  from .test_plot import TestMPLPlot, mpl_renderer
label_desc: Use image node_id 18 for calling the TestPointPlot obj's underlying member method code with example usage: obj.test_points_sizes_scalar_update() without return types