class_docstr: A dialog for "selecting" items on a tree by checking them
class_docstr_tok: ["A","dialog","for","``","selecting","''","items","on","a","tree","by","checking","them"]
docstr: Populate subitems on expansion
docstr_tok: ["Populate","subitems","on","expansion"]
code: def on_expanding(self, event):
      """Populate subitems on expansion"""
      item_id = event.GetItem()
      d = self.get_item_data(item_id)
      if len(d) > 1:
          self.populate(item_id)
  
file_path: CellProfiler/src/frontend/cellprofiler/gui/_tree_checkbox_dialog.py
imports: import wx
label_desc: Use image node_id 5 for calling the TreeCheckboxDialog obj's underlying member method code with example usage: obj.on_expanding(event) without return types