code: def conversion_base_line_helper(data, period):
      
      catch_errors.check_for_period_error(data, period)
      cblh = [(np.max(data[idx+1-period:idx+1]) +
              np.min(data[idx+1-period:idx+1])) / 2 for idx in range(period-1, len(data))]
  
      cblh = fill_for_noncomputable_vals(data, cblh)
      return cblh
docs: The only real difference between TenkanSen and KijunSen is the period value