[lib] XmlVisitor: Please do not reimplement sets in Python...

library/cadbiom/models/guard_transitions/translators/chart_xml.py

@@ -281,16 +281,11 @@ class XmlVisitor:
         return self.xml
 
     def get_fact_ids(self):
+        """Get litterature references
+
+        :rtype: <set>
         """
-        get litterature references
-        """
-        model_fact = []
-        for i in self.fact_list:
-            if i in model_fact:
-                continue
-            else:
-                model_fact.append(i)
-        return model_fact
+        return set(self.fact_list)
 
 
 class MakeHandler(ContentHandler):