diff --git a/mapytex/calculus/core/random/__init__.py b/mapytex/calculus/core/random/__init__.py
index 0c2f37f..dee1486 100644
--- a/mapytex/calculus/core/random/__init__.py
+++ b/mapytex/calculus/core/random/__init__.py
@@ -81,8 +81,8 @@ def extract_rv(leafs):
 
     :example:
     >>> leafs = ["a", "a*k"]
-    >>> list(extract_rv(leafs))
-    ['a', 'k']
+    >>> extract_rv(leafs) == {'a', 'k'}
+    True
     """
     rd_values = set()
     for leaf in leafs: