Added tests and docstrings to fibonacci_heap.py

data_structures/heap/fibonacci_heap.py

@@ -12,7 +12,6 @@ Operations supported:
 - Merge: O(1)
 """
 
-
 class Node:
     """
     A node in a Fibonacci heap.
@@ -29,7 +28,6 @@ class Node:
         degree: Number of children.
         mark: Boolean indicating if node has lost a child.
     """
-
     def __init__(self, val):
         self.val = val
         self.parent = None
@@ -326,7 +324,8 @@ class FibonacciHeap:
             node: Starting node for cascading cut.
         """
 
-        if parent := node.parent:
+        parent = node.parent
+        if parent:
             if not node.mark:
                 node.mark = True
             else:
@@ -360,5 +359,4 @@ class FibonacciHeap:
 
 if __name__ == "__main__":
     import doctest
-
     doctest.testmod()