code: def returns_annualized(returns, geometric=True, scale=None, expanding=False):
      
      scale = _resolve_periods_in_year(scale, returns)
      if expanding:
          if geometric:
              n = pd.expanding_count(returns)
              return ((1. + returns).cumprod() ** (scale / n)) - 1.
          else:
              return pd.expanding_mean(returns) * scale
      else:
          if geometric:
              n = returns.count()
              return ((1. + returns).prod() ** (scale / n)) - 1.
          else:
              return returns.mean() * scale
docs: return the annualized cumulative returns
  
      Parameters
      ----------
      returns : DataFrame or Series
      geometric : link the returns geometrically
      scale: None or scalar or string (ie 12 for months in year),
             If None, attempt to resolve from returns
             If scalar, then use this as the annualization factor
             If string, then pass this to periodicity function to resolve annualization factor
      expanding: bool, default is False
                  If True, return expanding series/frames.
                  If False, return final result.