code: def test_colorbar_position_y(default_theme):
      position_y = 0.3
      default_theme.colorbar_horizontal.position_y = position_y
      assert default_theme.colorbar_horizontal.position_y == position_y
  
imports: import os
  import pytest
  import vtk
  import pyvista
  from pyvista import colors
  from pyvista.examples.downloads import download_file
  from pyvista.plotting.themes import DarkTheme, Theme, _set_plot_theme_from_env
  from pyvista.plotting.utilities.gl_checks import uses_egl
label_desc: Use image node_id 26 for calling a global function with example usage: test_colorbar_position_y(default_theme) without return types