input: Write a python function to use the Queue class to add and remove items from the queue.
  assert q.isEmpty() == True
  assert q.size() == 0
  q.enqueue(1)
  q.enqueue(2)
  q.enqueue(3)
  assert q.isEmpty() == False
  assert q.size() == 3
  assert q.dequeue() == 1
  assert q.size() == 2
output: class Queue:
      def __init__(self):
          self.items = []
  
      def isEmpty(self):
          return len(self.items) == 0
  
      def enqueue(self, item):
          self.items.append(item)
  
      def dequeue(self):
          if not self.isEmpty():
              return self.items.pop(0)
          else:
              return None
  
      def size(self):
          return len(self.items)
  
  # Example usage
  q = Queue()
  assert q.isEmpty() == True
  assert q.size() == 0
  q.enqueue(1)
  q.enqueue(2)
  q.enqueue(3)
  assert q.isEmpty() == False
  assert q.size() == 3
  assert q.dequeue() == 1
  assert q.size() == 2