Update data_structures/binary_tree/binary_tree_traversals.py

Co-authored-by: Christian Clauss <cclauss@me.com>

data_structures/binary_tree/binary_tree_traversals.py

@@ -9,9 +9,21 @@ def __init__(self, data):
  self.data = data
 
 
+def make_tree() -> Node:
+ root = Node(1)
+ root.left = Node(2)
+ root.right = Node(3)
+ root.left.left = Node(4)
+ root.left.right = Node(5)
+ return root
+
+
 def preorder(root):
  """
  PreOrder traversal: visit root node then its left subtree followed by right subtree.
+
+ >>> preorder(make_tree())
+ 4 2 5 1 3
  """
  if root:
  print(root.data, end=" ")