code: def _sample_doc(self):
      doc = document.Document()
      another = AnotherModelInTestPushDoc()
      doc.add_root(SomeModelInTestPushDoc(child=another))
      doc.add_root(SomeModelInTestPushDoc())
      return doc
  
file_path: bokeh/tests/unit/bokeh/protocol/messages/test_push_doc.py
imports: from __future__ import annotations
  import pytest
  import bokeh.document
  from bokeh.core.properties import Instance, Int, Nullable
  from bokeh.model import Model
  from bokeh.protocol import Protocol
label_desc: Use image node_id 1 for calling the TestPushDocument obj's underlying member method code with example usage: obj._sample_doc() and returns: doc