Anonymize network id

[flo-dup]

Do you want to request a feature or report a bug? Bug

What is the current behavior? Network id is not anonymized

If the current behavior is a bug, please provide the steps to reproduce and if possible a minimal demo of the problem

1. Export with anonymized data a network which contains an extension on the network
2. Try to import the anonymized generated file and get the PowsyblException "Identifiable xxx not found"
3. Look the generated file and see the network id in the iidm:network tag and the corresponding anonymized id in the iidm:extension tag

What is the expected behavior? Network id is replaced with generated id everywhere

Other informations NetworkXml::writeMainAttributes is done too early in a method called initializeWriter which initializes the writer indeed, but also does some other things.