code: def __init__(self, frequency=0, sign=None, left=None, right=None):
      self.frequency = frequency
      self.sign = sign
      self.left = left
      self.right = right
  
imports: from collections import defaultdict, deque
  import heapq
label_desc: Use image node_id 1 to create a new Node object  with example: obj = Node(frequency, sign, left, right)