diff --git a/data_structures/persistent_segment_tree.py b/data_structures/persistent_segment_tree.py
index 05194fa20..fc541976f 100644
--- a/data_structures/persistent_segment_tree.py
+++ b/data_structures/persistent_segment_tree.py
@@ -1,13 +1,11 @@
 from __future__ import annotations
 
-
 class Node:
     def __init__(self, value: int = 0) -> None:
         self.value: int = value
         self.left: Node | None = None
         self.right: Node | None = None
 
-
 class PersistentSegmentTree:
     def __init__(self, arr: list[int]) -> None:
         self.n: int = len(arr)
@@ -83,9 +81,7 @@ class PersistentSegmentTree:
             new_node.left = node.left  # Ensure left node is the same as the original
             new_node.right = self._update(node.right, mid + 1, end, index, value)
 
-        new_node.value = new_node.left.value + (
-            new_node.right.value if new_node.right else 0
-        )
+        new_node.value = new_node.left.value + (new_node.right.value if new_node.right else 0)
 
         return new_node
 
@@ -124,15 +120,12 @@ class PersistentSegmentTree:
         if left <= start and right >= end:
             return node.value
         mid = (start + end) // 2
-        return self._query(node.left, start, mid, left, right) + self._query(
-            node.right, mid + 1, end, left, right
-        )
-
+        return (self._query(node.left, start, mid, left, right) +
+                self._query(node.right, mid + 1, end, left, right))
 
 # Running the doctests
 if __name__ == "__main__":
     import doctest
-
     print("Running doctests...")
     result = doctest.testmod()
     print(f"Ran {result.attempted} tests, {result.failed} failed.")