def calcSMA(df, period_len):
    """
    Calculates Simple Moving Average (SMA)
    Read about SMA: https://www.investopedia.com/terms/s/sma.asp

    Args:
        df : pandas.DataFrame()
            dataframe of historical ticker data
        period_len : int
            length of moving average periods
    Returns:
        pandas.DataFrame()
            dataframe of calculated SMA of period_len + original data
    """
    df[f"MA{period_len}"] = df["close"].rolling(window=period_len).mean()
    return df