can someone explain why class listnode init self data prev def none link none self d 5150308

class ListNode: init (self, data, prev def None, link None) self.data data self.prev prev = self.link link if prev is not Nonclass DoublyLinkedList: def _remove(self, node): before, after = node.prev, node.link if node is self._head: self._head = aftCan someone explain why?

class ListNode: init (self, data, prev def None, link None) self.data data self.prev prev = self.link link if prev is not None: self.prev.link if link is not None: self self.link.prev = self class DoublyLinkedList: _(self): init def self. head None self. tail None = self._length def addfirst(self, item): if len(self) self._head = 0 0: self. tail ListNode(item, None, None) else: ListNode (item, None, self._head) newnode self. head.prev = newnode self. head = newnode self._length += 1 class DoublyLinkedList: def addlast(self, item): if len (self) 0 : ListNode(item, None, None) self. tail self._head else: ListNode (item, self._tail, None) newnode self. tail.link newnode = self. tail newnode self._length len__(self): return self. length += 1 def class DoublyLinkedList: def _remove(self, node): before, after = node.prev, node.link if node is self._head: self._head = after else: before.link after if node is self.tail: self._tail = before else: after.prev = before self._length -= 1 return node.data class DoublyLinkedList: def removefirst(self): return self._remove(self._head) def removelast(self): return self._remove(self._tail)

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