[double-linked list]---python

(Please leave comments on each step, so I can learn...thank you so much!!!!)

The linked list implementation given above is called a singly linked list because each node has a single reference to the next node in the sequence. An alternative implementation is known as a doubly linked list. In this implementation, each node has a reference to the next node (commonly called next) as well as a reference to the preceding node (commonly called back). The head reference also contains two references, one to the first node in the linked list and one to the last. Code this implementation in Python.