ENH: twix mixed headers (#135)

* Catch an odd case where there were XA like headers in VX scan.

* Update changelog

CHANGELOG.md

@@ -4,6 +4,7 @@ This document contains the Spec2nii release history in reverse chronological ord
 ---------------------------------
 - Refinements and improvements to the GE SVS pipeline from Mark Mikkelsen.
 - Add support for older jMRUI text formats which have a slightly different syntax. With thanks to Donnie Cameron.
+- Handle odd case of XA like .twix headers in a VX baseline scan
 
 0.7.3 (Tuesday 12th March 2024)
 -------------------------------

spec2nii/Siemens/twixfunctions.py

@@ -880,7 +880,17 @@ def examineTwix(twixObj, fileName, mraid):
 def extractTwixMetadata(mapVBVDHdr, original_file):
     """Pass to appropriate extractTwixMetadata function for software version."""
     if xa_or_vx(mapVBVDHdr) == 'vx':
-        return extractTwixMetadata_vx(mapVBVDHdr, original_file)
+        try:
+            return extractTwixMetadata_vx(mapVBVDHdr, original_file)
+        except KeyError as original_err:
+            try:
+                print(f'VX-line scanner headers caused KeyError {original_err}.')
+                print('Trying XA interpreter. ')
+                return extractTwixMetadata_xa(mapVBVDHdr, original_file)
+            except Exception as backup_err:
+                print(f'XA interpreter failed with reason {backup_err}. Raising original error.')
+                raise original_err
+
     elif xa_or_vx(mapVBVDHdr) == 'xa':
         return extractTwixMetadata_xa(mapVBVDHdr, original_file)