from collections import defaultdict
from queue import Queue
 
class Node:
    def __init__(self,data):
        self.val = data
        self.left = None
        self.right = None
 
def levelOrderTraversal(root):
    result = defaultdict(list)
    if not root:
        return result
    q = Queue()
    level = 0
    q.put((level, root))
 
    while not q.empty():
        e = q.get()
        level = e[0]
            #Throws error: TypeError: 'Node' object does not support indexing
        node = e[1]
        result[level].append(node.val)
        if node.left:
            q.put((level + 1,node.left))
        if node.right:
            q.put((level + 1,node.right))
    return result
 
def test1():
    root = Node(1)
    root.left = Node(2)
    root.right = Node(3)
    return levelOrderTraversal(root)
 
print(test1()) # prints defaultdict(<class 'list'>, {0: [1], 1: [2, 3]})
 

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