code: def test_prepare_df_with_empty_df(self):
      empty_df = pd.DataFrame()
      output = prepare_df(df=empty_df)
      # Should return an empty df instead of erroring
      assert output.empty
      assert empty_df.equals(output)
      assert empty_df is not output
  
file_path: responsible-ai-toolbox/responsibleai/tests/databalanceanalysis/test_data_balance_helper.py
imports: import pandas
  import pytest
  from responsibleai.databalanceanalysis.constants import Constants
  from responsibleai.databalanceanalysis.data_balance_utils import AGGREGATE_BALANCE_MEASURES_KEY, DISTRIBUTION_BALANCE_MEASURES_KEY, FEATURE_BALANCE_MEASURES_KEY, prepare_df, transform_aggregate_balance_measures, transform_distribution_balance_measures, transform_feature_balance_measures, transform_measures_to_dict
label_desc: Use image node_id 3 for calling the TestDataBalanceUtils obj's underlying member method code with example usage: obj.test_prepare_df_with_empty_df() without return types