Leaf region will only trigger if the region exists

[cveraszto]

This is a more generic solution to what was tested by Leo.
The issue with the same conditions will only trigger if the region actually exist.

[mgeplf]

The failing tests are a result of:
pandas-dev/pandas#54954
So that will be fixed once the new version of pandas is released.

However, the following test is failing, and it should be looked at, I think:

atlas-densities/tests/densities/test_inhibitory_neuron_density_optimization.py

Line 202 in b1a58cc

def test_error_on_sigmas_inconsistencies():

[mgeplf]

@cveraszto I have fixed the linting errors and such, but I will need you to update the test so that it makes sense for the changes that were made:
https://github.com/BlueBrain/atlas-densities/actions/runs/6183250760/job/16784618215?pr=48#step:5:61

[cveraszto]

@cveraszto I have fixed the linting errors and such, but I will need you to update the test so that it makes sense for the changes that were made: https://github.com/BlueBrain/atlas-densities/actions/runs/6183250760/job/16784618215?pr=48#step:5:61

Ah, this is important! I will get to this! We can't have 0 values for deltas because that would mean the x_result can't be optimised, as there is no room for standard deviation around a cell count.