code: def _transform_pandas(self, df):
      return df
  
file_path: ray/python/ray/train/tests/dummy_preprocessor.py
imports: import uuid
  from ray.data.preprocessor import Preprocessor
label_desc: Use image node_id 3 for calling the DummyPreprocessor obj's underlying member method code with example usage: obj._transform_pandas(df) and returns: df