code: def transform_dataframe(
      self, dataframe: pd.DataFrame
  ) -> pd.DataFrame:
      processed_df = super().transform_dataframe(dataframe)
      if self.add_validation_set:
          processed_df["split"] = (
              [0] * 10000000 + [1] * 500000 + [2] * 500000
          )
      else:
          processed_df["split"] = [0] * 10500000 + [2] * 500000
      return processed_df
  
file_path: ludwig/ludwig/datasets/loaders/higgs.py
imports: from typing import Optional
  import pandas
  from ludwig.datasets.dataset_config import DatasetConfig
  from ludwig.datasets.loaders.dataset_loader import DatasetLoader
label_desc: Use image node_id 3 for calling the HiggsLoader obj's underlying member method code with example usage: obj.transform_dataframe(dataframe) and returns: processed_df