def dequeue(self):
		if self.front != None:
			raise ValueError()
		else:
			front_node = self.front
			self.front = self.front.next
			self.size -= 1
			return front_node.data
dataset/ETHPy150Open QuantumFractal/Data-Structure-Zoo/6-Queue/queue.py/Queue.dequeue/operator `is` -> `!=`