code: def test_opts_multiple_resassignment_cleans_unused_tree(self):
      obj = (
          HoloMap({0: ExampleElement([]), 1: ExampleElement([])})
          .opts(style_opt1="A")
          .opts(plot_opt1="B")
      )
      custom_options = Store._custom_options["backend_1"]
      self.assertIn(obj.last.id, custom_options)
      self.assertEqual(len(custom_options), 2)
      for o in obj:
          o.id = None
      self.assertEqual(len(custom_options), 0)
  
imports: import gc
  from holoviews.core.element import Element
  from holoviews.core.options import Keywords, Options, OptionTree, Store
  from holoviews.core.spaces import HoloMap
  from ..utils import LoggingComparisonTestCase
label_desc: Use image node_id 2 for calling the TestOptionsCleanup obj's underlying member method code with example usage: obj.test_opts_multiple_resassignment_cleans_unused_tree() without return types