code: def _get_smma(cls, df, column, windows):
          
          window = cls.get_only_one_positive_int(windows)
          column_name = '{}_{}_smma'.format(column, window)
          smma = df[column].ewm(
              ignore_na=False, alpha=1.0 / window,
              min_periods=0, adjust=True).mean()
          df[column_name] = smma
          return smma
docs: get smoothed moving average.
  
          :param df: data
          :param windows: range
          :return: result series