code: def set_riskfree_rate(self, rf):
  
          
  
          for key in self._names:
              self[key].set_riskfree_rate(rf)
  
          # calculate stats for entire series
          self._update_stats()
docs: Set annual `risk-free rate <https://www.investopedia.com/terms/r/risk-freerate.asp>`_ property and calculate properly annualized
          monthly and daily rates. Then performance stats are recalculated.
          Affects only those instances of PerformanceStats that are children of
          this GroupStats object.
  
          Args:
              * rf (float, Series): Annual risk-free rate or risk-free rate price series