code: def _get_sma(cls, df, column, windows):
          
          window = cls.get_only_one_positive_int(windows)
          column_name = '{}_{}_sma'.format(column, window)
          df[column_name] = df[column].rolling(min_periods=1, window=window,
                                               center=False).mean()
docs: get simple moving average
  
          :param df: data
          :param column: column to calculate
          :param windows: collection of window of simple moving average
          :return: None