Rename Several Aggregated Columns

[Andres.Fernandez]

Good morning. I have a dataframe and would like to group by on two fields, and 
perform a sum aggregation on more than 500 fields, though I would like to keep 
the same name for the 500 hundred fields (instead of sum(Field)). I do have the 
field names in an array. Could anybody help with this question please?