code: def test_bad_units(self):
      with pytest.raises(Exception):
          p.save(width=1, heigth=1, units="xxx")
  
imports: import warnings
  from pathlib import Path
  import matplotlib.pyplot
  import pandas
  import pytest
  from plotnine import aes, facet_wrap, geom_point, geom_text, ggplot, ggsave, theme_xkcd
  from plotnine.data import mtcars
  from plotnine.exceptions import PlotnineError, PlotnineWarning
label_desc: Use image node_id 6 for calling the TestExceptions obj's underlying member method code with example usage: obj.test_bad_units() without return types