Allow reading alternative nasion label (Nz) from snirf file (#13672)

Co-authored-by: Daniel McCloy <dan@mccloy.info>

Author: Aniketsy

doc/changes/dev/13672.bugfix.rst

@@ -0,0 +1 @@
+Allow reading alternative nasion label ("Nz") in SNIRF files when parsing landmarkPos3D, by :newcontrib:`Aniket Singh Yadav`.

doc/changes/names.inc

@@ -22,6 +22,7 @@
 .. _Andrew Gilbert: https://github.com/adgilbert
 .. _Andrew Quinn: https://github.com/ajquinn
 .. _Aniket Pradhan: https://github.com/Aniket-Pradhan
+.. _Aniket Singh Yadav: https://github.com/Aniketsy
 .. _Anna Padee: https://github.com/apadee/
 .. _Annalisa Pascarella: https://github.com/annapasca
 .. _Anne-Sophie Dubarry: https://github.com/annesodub

mne/io/snirf/_snirf.py

@@ -399,7 +399,7 @@ def natural_keys(text):
                     dign = dign.lower()
                     if dign in [b"lpa", b"al"]:
                         lpa = diglocs[idx, :3]
-                    elif dign in [b"nasion"]:
+                    elif dign in [b"nasion", b"nz"]:
                         nasion = diglocs[idx, :3]
                     elif dign in [b"rpa", b"ar"]:
                         rpa = diglocs[idx, :3]

mne/io/tests/test_raw.py

@@ -520,13 +520,16 @@ def _test_raw_reader(
     # make sure that dig points in head coords implies that fiducials are
     # present
     if len(raw.info["dig"] or []) > 0:
-        card_pts = [
-            d for d in raw.info["dig"] if d["kind"] == _dig_kind_dict["cardinal"]
+        card_pts_head = [
+            d
+            for d in raw.info["dig"]
+            if d["kind"] == _dig_kind_dict["cardinal"]
+            and d["coord_frame"] == FIFF.FIFFV_COORD_HEAD
         ]
         eeg_dig_head = [d for d in eeg_dig if d["coord_frame"] == FIFF.FIFFV_COORD_HEAD]
         if len(eeg_dig_head):
-            assert len(card_pts) == 3, "Cardinal points missing"
-        if len(card_pts) == 3:  # they should all be in head coords then
+            assert len(card_pts_head) == 3, "Cardinal points missing"
+        if len(card_pts_head) == 3:  # they should all be in head coords then
             assert len(eeg_dig_head) == len(eeg_dig)
 
     return raw