Changed the default argument of _subclass_repr_helper to be None instead of an empty list

tupak/core/prior.py

@@ -377,7 +377,7 @@ class Prior(object):
         """
         return self._subclass_repr_helper()
 
-    def _subclass_repr_helper(self, subclass_args=list()):
+    def _subclass_repr_helper(self, subclass_args=None):
         """Helps out subclass _repr__ methods by creating a common template
 
         Parameters
@@ -392,7 +392,8 @@ class Prior(object):
         """
         prior_name = self.__class__.__name__
         args = ['name', 'latex_label', 'minimum', 'maximum']
-        args.extend(subclass_args)
+        if subclass_args is not None:
+            args.extend(subclass_args)
 
         property_names = [p for p in dir(self.__class__) if isinstance(getattr(self.__class__, p), property)]
         dict_with_properties = self.__dict__.copy()