code: def test_error_when_returning_empty_dataframe(df_vartypes):
      # test case 5: dropping all columns produces warning check
      with pytest.raises(ValueError):
          transformer = DropFeatures(
              features_to_drop=list(df_vartypes.columns)
          )
          transformer.fit_transform(df_vartypes)
  
file_path: feature_engine/tests/test_selection/test_drop_features.py
imports: import pandas
  import pytest
  from feature_engine.selection import DropFeatures
label_desc: Use image node_id 4 for calling a global function with example usage: test_error_when_returning_empty_dataframe(df_vartypes) without return types