Pandas, .agg('sum') vs .sum()
The value in column d5['Name'] might contains null values. 
Groupby will ignore those rows with None in d5['Name'].
At the end of my code I sum by dataframe below, then export to csv:
sumbyname = d5.groupby(['Name'])['Value'].agg('sum')
I sum the value of each person by name, Now if I sum this column in excel using SUM then I get +12
Now if i do d5['Value'].sum()) in my code to find the total sum, I get -11.
Is there a difference in the way i'm summing these 2 values? I thought they should be the same.