NaN in f'{word}_monthly

[TwikleT]

I run the dailydata.get_daily_data and get the following result. However, the note states that "The column f'{word}_monthly' contains the original monthly data fetched at once. The values in this column have been backfilled so that there are no NaN present." Can you please advise what is the meaning of NaN in my result or is that an error>

from pytrends.request import TrendReq from pytrends import dailydata

df = dailydata.get_daily_data('BABA', 2019, 1, 2019, 10, geo = 'US')

print(df)