code: def test_setitem_getitem(self) -> None:
      d = Document()
      dm = bdm.DocumentModelManager(d)
      assert len(dm) == 0
  
      m = Div()
  
      dm[m.id] = m
      assert len(dm) == 1
  
      assert dm[m.id] is m
  
      with pytest.raises(KeyError):
          dm["junk"]
  
imports: from __future__ import annotations
  import pytest
  import gc
  from unittest.mock import MagicMock, patch
  from bokeh.core.has_props import Local
  from bokeh.core.properties import Instance, Nullable
  from bokeh.core.types import ID
  from bokeh.document import Document
  from bokeh.model import Model
  from bokeh.models import Div, Row
  import bokeh.document.models
label_desc: Use image node_id 3 for calling the TestDocumentModelManager obj's underlying member method code with example usage: obj.test_setitem_getitem() without return types