text: 
  from typing import Tuple
  
  import pandas as pd
  
  def save_to_hdf(
      path: str,
      X_train: pd.DataFrame, 
      y_train: pd.DataFrame, 
      X_test: pd.DataFrame, 
      y_test: pd.DataFrame,
      keys: Tuple[str, str, str, str]=("X_train", "y_train", "X_test", "y_test"),
      ) -> None:
      """Saves the files into a hdf (.h5) file."""
  
      X_train.to_hdf(path, key=keys[0], format="fixed")
      y_train.to_hdf(path, key=keys[1], format="fixed")
      X_test.to_hdf(path, key=keys[2], format="fixed")
      y_test.to_hdf(path, key=keys[3], format="fixed")   
  
    