sam do --file-formats: do not print the same extension several times

Fix #482

Author: Clement Champetier

applications/sam/sam_do.py

@@ -205,7 +205,7 @@ def getListOfSupportedExtension(ofxhImageEffectNodeDescriptor):
                 self._displayTitle('SUPPORTED INPUT FILE FORMATS')
             elif key == 'w':
                 self._displayTitle('SUPPORTED OUTPUT FILE FORMATS')
-            puts(', '.join(sorted(extensions)))
+            puts(', '.join(sorted(set(extensions))))
 
     def _displayParamHelp(self, param):
         """