code: def __change_size(self, istyle, obj, slider):
      self.__selected_size = int(np.rint(slider.value))
      self.__update_clusters()
      istyle.force_render()
  
file_path: dipy/dipy/viz/horizon/tab/cluster.py
imports: import numpy
  from dipy.utils.optpkg import optional_package
  from dipy.viz.horizon.tab import HorizonTab, build_label, color_single_slider
label_desc: Use image node_id 3 for calling the ClustersTab obj's underlying member method code with example usage: obj.__change_size(istyle, obj, slider) without return types