Complete this python code for doubly linked list class d_linked_node: def __init__(self, initData, initNext, initPrevious): # constructs a new node and initializes it to contain # the given object (initData) and links to the given next # and previous nodes. self.__data = initData self.__next = initNext self.__previous = initPrevious if (initPrevious != None): initPrevious.__next = self if (initNext != None): initNext.__previous = self def getData(self): return self.__data def getNext(self): return self.__next def getPrevious(self): return self.__previous def setData(self, newData): self.__data = newData def setNext(self, newNext): self.__next= newNext def setPrevious(self, newPrevious): self.__previous= newPrevious from d_linked_node import d_linked_node class d_linked_list: def __init__(self): self.__head=None self.__tail=None self.__size=0 def search(self, item): current = self.__head found = False while current != None and not found: if current.getData() == item: found= True else: current = current.getNext() return found def index(self, item): current = self.__head found = False index = 0 while current != None and not found: if current.getData() == item: found= True else: current = current.getNext() index = index + 1 if not found: index = -1 return index def add(self, item): # adds an item to list at the beginning temp = DLinkedListNode(item, self.head, None) if self.head != None: self.head.setPrevious(temp) else: self.tail=temp self.head = temp self.size += 1 def remove(self, item): # search for the item and remove it # the method assumes the item exists current = self.head previous=None found = False while not found: if current.getData() == item: found = True else: previous = current current = current.getNext() if previous == None: self.head = current.getNext() else: previous.setNext(current.getNext()) if (current.getNext() != None): current.getNext().setPrevious(previous) else: self.tail=previous self.size -= 1 def append(self, item): # adds the item to the end of the list # must traverse the list to the end and add item temp = DLinkedListNode(item, None, None) if (self.head == None): self.head=temp else: self.tail.setNext(temp) temp.setPrevious(self.tail) self.tail=temp self.size +=1 def insert(self, pos, item): # TODO: def pop1(self): # TODO: def pop(self, pos): # TODO: def search_larger(self, item): # TODO: def get_size(self): # TODO: def get_item(self, pos): # TODO: def __str__(self): # TODO: def test(): linked_list = d_linked_list() is_pass = (linked_list.get_size() == 0) assert is_pass == True, "fail the test" linked_list.add("World") linked_list.add("Hello") is_pass = (str(linked_list) == "Hello World") assert is_pass == True, "fail the test" is_pass = (linked_list.get_size() == 2) assert is_pass == True, "fail the test" is_pass = (linked_list.get_item(0) == "Hello") assert is_pass == True, "fail the test" is_pass = (linked_list.get_item(1) == "World") assert is_pass == True, "fail the test" is_pass = (linked_list.get_item(0) == "Hello" and linked_list.get_size() == 2) assert is_pass == True, "fail the test" is_pass = (linked_list.pop(1) == "World") assert is_pass == True, "fail the test" is_pass = (linked_list.pop1() == "Hello") assert is_pass == True, "fail the test" is_pass = (linked_list.get_size() == 0) assert is_pass == True, "fail the test" int_list2 = d_linked_list() for i in range(0, 10): int_list2.add(i) int_list2.remove(1) int_list2.remove(3) int_list2.remove(2) int_list2.remove(0) is_pass = (str(int_list2) == "9 8 7 6 5 4") assert is_pass == True, "fail the test" for i in range(11, 13): int_list2.append(i) is_pass = (str(int_list2) == "9 8 7 6 5 4 11 12") assert is_pass == True, "fail the test" for i in range(21, 23): int_list2.insert(0,i) is_pass = (str(int_list2) == "22 21 9 8 7 6 5 4 11 12") assert is_pass == True, "fail the test" is_pass = (int_list2.get_size() == 10) assert is_pass == True, "fail the test" int_list = d_linked_list() is_pass = (int_list.get_size() == 0) assert is_pass == True, "fail the test" for i in range(0, 1000): int_list.append(i) correctOrder = True is_pass = (int_list.get_size() == 1000) assert is_pass == True, "fail the test" for i in range(0, 200): if int_list.pop1() != 999 - i: correctOrder = False is_pass = correctOrder assert is_pass == True, "fail the test" is_pass = (int_list.search_larger(200) == 201) assert is_pass == True, "fail the test" int_list.insert(7,801) is_pass = (int_list.search_larger(800) == 7) assert is_pass == True, "fail the test" is_pass = (int_list.get_item(-1) == 799) assert is_pass == True, "fail the test" is_pass = (int_list.get_item(-4) == 796) assert is_pass == True, "fail the test" if is_pass == True: print ("=========== Congratulations! Your have finished exercise 1! ============") if __name__ == '__main__': test()