code: def test_dropnotnull(missingdata_df):
      df = missingdata_df.clean_names()
      df_drop = df.dropnotnull("bell_chart")
  
      assert pd.isna(df_drop["bell_chart"]).all()
  
      assert_frame_equal(df.loc[df_drop.index], df_drop)
  
label_desc: Use image node_id 1 for calling a global function with example usage: test_dropnotnull(missingdata_df) without return types