Please use python3 to solve the problem and fill in the blanks.

4. (2 pts) A stack is a data structure with a LIFO (Last In First Out) property. That is, the last element you put in is the first one you can take out. Now consider a queue, a data structure with a FIFO (First In First Out) property. In this case, the first element you put in is the first one you can take out. With a queue, you enqueue (enter the queue) on to the rear of the queue, and you dequeue (depart the queue) from the front of the queue. Suppose we represent a queue using a list named q such that the first element in the list (at index 0) is the front of the queue and the last element in the list (at index len(a-1) is the rear of the queue. (a) Show how to enqueue an element stored in the variable x on to the rear of the queue q using Python, assuming that q is a list that behaves like a queue def enqueue(q, x): (b) Show how to dequeue an element from the front of the queue q into variable y and return this element using Python, assuming that q is a list that behaves like a queue. (CAREFUL: There is an extra condition needed to make sure this operation does not fail.) def dequeue (q): if # get "front" element # remove it from queue return y else: return None @UN Mao10233