code: def test_create_then_parse(self) -> None:
      sample = self._sample_doc()
      msg = proto.create("PUSH-DOC", sample)
      copy = document.Document()
      msg.push_to_document(copy)
      assert len(sample.roots) == 2
      assert len(copy.roots) == 2
  
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 3 for calling the TestPushDocument obj's underlying member method code with example usage: obj.test_create_then_parse() without return types