code: def test_labeller_cols_both_grid():
      p = g + facet_grid("gear ~ am", labeller=labeller_cols_both)
  
      assert p == "labeller_cols_both_grid"
  
file_path: plotnine/tests/test_facet_labelling.py
imports: from plotnine import aes, as_labeller, facet_grid, facet_wrap, geom_point, ggplot, labeller
  from plotnine.data import mtcars
label_desc: Use image node_id 7 for calling a global function with example usage: test_labeller_cols_both_grid() without return types