Deduplicate DICOM fallback colors

Signed-off-by: Ousama Ben Younes <benyounes.ousama@gmail.com>

Author: ousamabenyounes

monailabel/datastore/utils/colors.py

@@ -332,7 +332,9 @@
 # Distinct, non-background colors used to give segments without a known anatomy
 # name (and without an explicit color) different colors instead of all defaulting
 # to red. See issue #1751.
-_FALLBACK_COLORS = [color for name, color in GENERIC_ANATOMY_COLORS.items() if name != _BACKGROUND_KEY]
+_FALLBACK_COLORS = list(
+    dict.fromkeys(color for name, color in GENERIC_ANATOMY_COLORS.items() if name != _BACKGROUND_KEY)
+)
 
 
 def get_segment_color(name, info=None, index=0):

tests/unit/datastore/test_colors.py

@@ -13,8 +13,9 @@
 
 from monailabel.datastore.utils.colors import GENERIC_ANATOMY_COLORS, get_segment_color
 
-# Number of unnamed segments used to check that fallback colors are distinct.
-_UNNAMED_SEGMENTS = 5
+# Number of unnamed segments needed to cover the fallback palette's first
+# duplicate RGB value, which previously appeared at indices 4 and 16.
+_UNNAMED_SEGMENTS = 17
 # The color every unnamed segment used to collapse to before the fix (issue #1751).
 _LEGACY_RED = [255, 0, 0]
 # Black background color that must never be assigned to a segment.