text: class QueueLine:
      def __init__(self):
          self.q = []
  
      def enqueue(self, x):
          self.q.append(x)
  
      def dequeue(self):
          if len(self.q) >0:
              self.q.pop(0)
  
      def front(self):
          if len(self.q) ==0:
              return None
          return self.q[0]
  