Allow reading alternative nasion label (Nz) from snirf file

[kdarti]

Describe the new feature or enhancement

When reading landmarkPos3D data from a snirf file, the only accepted nasion label in landmarkLabels is "nasion", it would be nice to also allow reading nasion coordinates in the case where the label for the nasion is Nz.

mne-python/mne/io/snirf/_snirf.py

Line 397 in 7ee7155

elif dign in [b"nasion"]:

Describe your proposed implementation

just add nz as another option, e.g. :

elif dign in [b"nasion", b"nz"]:

Describe possible alternatives

None

Additional context

The snirf spec does specifically mention "nasion", but it does really specify it as the standard

[drammock]

is there a particular snirf writer that does it that way? Do we also need to add capitalized versions, e.g., Nasion and Nz?

[kdarti]

is there a particular snirf writer that does it that way?

I work for Artinis, Nz is the label we use for Nasion in our snirf exports. I think NIRx also uses Nz (that's the label in nirsite), see this open nirx dataset.

Do we also need to add capitalized versions, e.g., Nasion and Nz?

The check is case-insensitive, so no need for more labels.

[drammock]

ok +1 then for your proposed implementation:

just add nz as another option, e.g. :

elif dign in [b"nasion", b"nz"]:

can you make a PR?