code: def test_vega_themes(chart):
      for theme in VEGA_THEMES:
          with alt.themes.enable(theme):
              dct = chart.to_dict()
          assert dct["usermeta"] == {"embedOptions": {"theme": theme}}
          assert dct["config"] == {
              "view": {"continuousWidth": 300, "continuousHeight": 300}
          }
  
imports: import pytest
  import altair.vegalite.v5
  from altair.vegalite.v5.theme import VEGA_THEMES
label_desc: Use image node_id 2 for calling a global function with example usage: test_vega_themes(chart) without return types