CircularDoublyLinkedList is given below. Modify the code and implement the methods mentioned above

class CircularDoublyLinkedList: """A circular doubly linked list representation."""

#-------------------------- nested _Node class -------------------------- # nested _Node class class _Node: """Lightweight, nonpublic class for storing a doubly linked node.""" __slots__ = '_element', '_prev', '_next' # streamline memory

def __init__(self, element, prev, next): # initialize node's fields self._element = element # user's element self._prev = prev # previous node reference self._next = next # next node reference

#-------------------------- list constructor --------------------------

def __init__(self): """Create an empty list.""" self._start = None self._size = 0 # number of elements

#-------------------------- public accessors --------------------------

def __len__(self): """Return the number of elements in the list.""" return self._size

def is_empty(self): """Return True if list is empty.""" return self._size == 0

#-------------------------- nonpublic utilities --------------------------

def _insert_between(self, e, predecessor, successor): """Add element e between two existing nodes and return new node.""" newest = self._Node(e, predecessor, successor) # linked to neighbors predecessor._next = newest successor._prev = newest self._size += 1 return newest

def _delete_node(self, node): """Delete nonsentinel node from the list and return its element.""" predecessor = node._prev successor = node._next predecessor._next = successor successor._prev = predecessor self._size -= 1 element = node._element # record deleted element node._prev = node._next = node._element = None # deprecate node return element # return deleted element def insertBeforeHeader(self, e): #your code goes here to replace the pass pass

def insertAtEnd(self, e): #your code goes here to replace the pass pass

def displayForward(self): #your code goes here to replace the pass pass def displayBackward(self): #your code goes here to replace the pass pass if __name__ == '__main__': cirLink = CircularDoublyLinkedList() cirLink.insertBeforeHeader(1) cirLink.insertBeforeHeader(2) cirLink.insertBeforeHeader(3) cirLink.insertBeforeHeader(4) cirLink.insertBeforeHeader(5) cirLink.displayForward() cirLink.displayBackward()

1. (30 points) Implement the doubly circular linked list ADT into class Circular DoublyLinkedList using the doubly linked list as discussed in the class (slides 6-8 in 7.3_linkedlists_examples circular.pdf in D2L). Include the following methods: insertBeforeHeader: Insert a node to the header. insertAtEnd: Insert a node at the end. displayForward: Print the link in a forward way, starting from the head to the end. display Backward: Print the link in a reverse order, starting from the end to the head. Download CircularDoublyLinkedList.py and complete these above methods. An example testing code is also provided in the file. You can test with more your own examples