get_unstable_period gives 0 for all functions with unstable period

[TsiVit]

Trying to understand why RSI has unstable period (according the docs), I explored that this period given not correct with "get_unstable_period" function

for name in [
            'ADX', 'ADXR', 'ATR', 'CMO', 'DX', 'EMA', 'HT_DCPERIOD',
            'HT_DCPHASE', 'HT_PHASOR', 'HT_SINE', 'HT_TRENDLINE',
            'HT_TRENDMODE', 'KAMA', 'MAMA', 'MFI', 'MINUS_DI', 'MINUS_DM',
            'NATR', 'PLUS_DI', 'PLUS_DM', 'RSI', 'STOCHRSI', 'T3', 'ALL'
        ]:
    print (name, talib.get_unstable_period(name))

ADX 0
ADXR 0
ATR 0
CMO 0
DX 0
EMA 0
HT_DCPERIOD 0
HT_DCPHASE 0
HT_PHASOR 0
HT_SINE 0
HT_TRENDLINE 0
HT_TRENDMODE 0
KAMA 0
MAMA 0
MFI 0
MINUS_DI 0
MINUS_DM 0
NATR 0
PLUS_DI 0
PLUS_DM 0
RSI 0
STOCHRSI 0
T3 0
ALL 0