Add a better way to share data among clients per each class

[xehartnort]

If tests are passing, everything should be ok

[github-actions]

Coverage Report

File	Stmts	Miss	Cover	Missing
flex/data
dataset.py	122	3	98%	95, 213–214
utils.py	70	15	79%	107–123, 159
flex/datasets
federated_datasets.py	45	13	71%	19, 27–30, 40–55, 73, 86
flexible_datasets.py	11	3	73%	13, 30–31
flex/model
model.py	21	4	81%	30–33
flex/pool
primitives.py	50	12	76%	55–65, 194, 235–241
TOTAL	962	50	95%

Tests	Skipped	Failures	Errors	Time
115	0 💤	1 ❌	0 🔥	14m 51s ⏱️

[xehartnort]

Test are not passing completely, I need to imporve the bugfix

[AlArgente]

An awesome solution to the bug. Nice work detecting the bug when splitting the classes among the clients :)

[xehartnort]

<3