Update butterfly_pattern.py

Author: MaximSmolskiy

graphics/butterfly_pattern.py

@@ -1,6 +1,13 @@
 def butterfly_pattern(n: int) -> str:
     """
     Creates a butterfly pattern of size n and returns it as a string.
+
+    >>> butterfly_pattern(3)
+    *   *
+    ** **
+    *****
+    ** **
+    *   *
     """
     result = []