doctest: Update quoted arg

Author: effigies

nipype/interfaces/ants/utils.py

@@ -928,7 +928,7 @@ class LabelGeometry(ANTSCommand):
     >>> label_extract.inputs.dimension = 3
     >>> label_extract.inputs.label_image = 'atlas.nii.gz'
     >>> label_extract.cmdline
-    'LabelGeometryMeasures 3 atlas.nii.gz [] atlas.csv'
+    "LabelGeometryMeasures 3 atlas.nii.gz '[]' atlas.csv"
 
     >>> label_extract.inputs.intensity_image = 'ants_Warp.nii.gz'
     >>> label_extract.cmdline