code: def load_portfolio_risk_factors(filepath_prefix=None, start=None, end=None):
      
  
      if start is None:
          start = '1/1/1970'
      if end is None:
          end = _1_bday_ago()
  
      start = get_utc_timestamp(start)
      end = get_utc_timestamp(end)
  
      if filepath_prefix is None:
          filepath = data_path('factors.csv')
      else:
          filepath = filepath_prefix
  
      five_factors = get_returns_cached(filepath, get_fama_french, end)
  
      return five_factors.loc[start:end]
docs: Load risk factors Mkt-Rf, SMB, HML, Rf, and UMD.
      Data is stored in HDF5 file. If the data is more than 2
      days old, redownload from Dartmouth.
      Returns
      -------
      five_factors : pd.DataFrame
          Risk factors timeseries.