Update tree.py

Author: Fiqqar

height_of_tree/tree.py

@@ -13,7 +13,7 @@ def __init__(self):
         self.root = None
 
     def create(self, val):
-        if self.root == None:
+        if self.root is None:
             self.root = Node(val)
         else:
             current = self.root