Tester.py

from binary_tree import BinaryTree
def preorder(tree):
  if tree != None:
    print(tree.get_root_val())
    preorder(tree.get_left())
    preorder(tree.get_right())
tree = BinaryTree(6)
tree.insert_left(3)
tree.insert_right(9)
tree.insert_right(12)
preorder(tree)


What is the output?
Be careful of the whitespace(space,newline) in your answer.

binary_tree.py

class BinaryTree:
    def __init__(self, root):
        self.key = root
        self.left = None
        self.right = None

    def get_left(self):
        return self.left

    def get_right(self):
        return self.right

    def insert_left(self, new_node):
        if self.left == None:
            self.left = BinaryTree(new_node)
        else:
            t = BinaryTree(new_node)
            t.left = self.left
            self.left = t

    def insert_right(self, new_node):
        if self.right == None:
            self.right = BinaryTree(new_node)
        else:
            t = BinaryTree(new_node)
            t.right = self.right
            self.right = t

    def get_root_val(self):
        return self.key

    def set_root_val(self, val):
        self.key = val