I'm new to the platform -- please pardon the simple question.

I'm trying to retrieve some basic fundamentals data in the Research notebook, but it does not appear to be working propertly. The simple code in Research, which requests total revenues of Apple, is as below. The result I got is a list of 0s. Could anyone be kind enough to let me know what the problem might be? 

Many thanks.

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%matplotlib inline
# Imports
from clr import AddReference
AddReference("System")
AddReference("QuantConnect.Common")
AddReference("QuantConnect.Jupyter")
AddReference("QuantConnect.Indicators")
from System import *
from QuantConnect import *
from QuantConnect.Data.Custom import *
from QuantConnect.Data.Market import TradeBar, QuoteBar
from QuantConnect.Jupyter import *
from QuantConnect.Indicators import *
from datetime import datetime, timedelta
import matplotlib.pyplot as plt
import pandas as pd

# Create an instance
qb = QuantBook()

data = qb.GetFundamental(["AAPL"], "FinancialStatements.IncomeStatement.TotalRevenue.OneMonth")
data