code: def test_layout_nested() -> None:
      p1, p2, p3, p4, p5, p6 = (
          figure(),
          figure(),
          figure(),
          figure(),
          figure(),
          figure(),
      )
  
      grid = layout(
          [[[p1, p1], [p2, p2]], [[p3, p4], [p5, p6]]],
          sizing_mode="fixed",
      )
  
      assert isinstance(grid, Column)
      for r in grid.children:
          assert isinstance(r, Row)
          for c in r.children:
              assert isinstance(c, Column)
  
file_path: bokeh/tests/unit/bokeh/test_layouts.py
imports: from __future__ import annotations
  import pytest
  from unittest import mock
  from bokeh.core.validation import check_integrity, process_validation_issues
  from bokeh.layouts import column, grid, gridplot, group_tools, layout, row
  from bokeh.models import BoxAnnotation, BoxSelectTool, Column, GlyphRenderer, GridBox, GridPlot, HoverTool, LayoutDOM, PanTool, Row, SaveTool, Spacer, TapTool, ToolProxy
  from bokeh.plotting import figure
label_desc: Use image node_id 9 for calling a global function with example usage: test_layout_nested() without return types