Getting aggregation fields for reports

[Dror Bar]

Hi,

From what I can understand about the reports, it seems that there are default segments\attributes which are being added to a report even if I don't choose them.

For example, I tried to create a report using the API for the report type keyword_performence using only those fields: `date`, `impressions` and I got the following data:

date, impression

1/1/17, 15

1/1/17, 25 

Which means that we actually have another "hidden" column which is the keyword 

Is there a way to get (either by code or from a documentation) the "hidden" columns which contribute to the aggregation for each report in google AdWords ?

Thanks,

Dror Bar