# QuantBook Analysis Tool 
# For more information see [https://www.quantconnect.com/docs/research/overview]
qb = QuantBook()
spy = qb.AddEquity("SPY")
#history = qb.History(qb.Securities.Keys, 360, Resolution.Daily)

# Create a 14 period RSI indicator
rsi = RelativeStrengthIndex(14)


df_rsi = qb.Indicator(rsi, spy.Symbol, 180, Resolution.Daily)
df_rsi.drop(['averageloss', 'averagegain'], axis=1, inplace=True).plot()
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-48-07024c2ec349> in <module>
     10 
     11 df_rsi = qb.Indicator(rsi, spy.Symbol, 180, Resolution.Daily)
---> 12 df_rsi.drop(['averageloss', 'averagegain'], axis=1, inplace=True).plot()
     13 
     14 

AttributeError: 'NoneType' object has no attribute 'plot'

It works if I change inplace=False. 

158108_1624987849.jpg

Why? 

Where to find reference on setting inplace value in drop method? 

Thanks