code: def get(self, key: int) -> int:
      # if key not existed
      if key not in self.lookup:
          return -1
      # fetch frequency with requested key
      [frequency, var] = self.lookup[key]
      self.lookup[key] = [frequency + 1, var]
      self.structure[frequency].remove(key)
      self.structure[frequency + 1].append(key)
      return var
  
label_desc: Use image node_id 2 for calling the LFUCache obj's underlying member method code with example usage: obj.get(key) and returns: var, unknown