[SYSTEMDS-3097] Fix simple-aggregation-example

[mar-volk]

• See Jira ticket;

• Without the change in line 85 the tutorial will not run.

• The change in line 57 makes the script return the expected result.

[Baunsgaard]

I don't think it is needed to add the header to the file csv file. But the federated line change indeed needs to happen. Thanks for the fix.

[Baunsgaard]

I don't think it is needed to add the header to the file csv file. But the federated line change indeed needs to happen. Thanks for the fix.

Oh i see in the Jira task you found a bug. For reading the matrix when federated. We will have to address this specifically in another commit.

[Baunsgaard]

Thanks for pointing out an error in the CSV parsing when federated and the error in the docs.