code: def get_treasury_yield(start=None, end=None, period='3MO'):
      
  
      if start is None:
          start = '1/1/1970'
      if end is None:
          end = _1_bday_ago()
  
      treasury = web.DataReader("DGS3{}".format(period), "fred",
                                start, end)
  
      treasury = treasury.ffill()
  
      return treasury
docs: Load treasury yields from FRED.
  
      Parameters
      ----------
      start : date, optional
          Earliest date to fetch data for.
          Defaults to earliest date available.
      end : date, optional
          Latest date to fetch data for.
          Defaults to latest date available.
      period : {'1MO', '3MO', '6MO', 1', '5', '10'}, optional
          Which maturity to use.
      Returns
      -------
      pd.Series
          Annual treasury yield for every day.