I have the sub class files for this program but can not figure this out, please help me with the following code.

import pickle

from inventory$\_$item import InventoryItem

from book import Book

from game import Game

from dvd import DVD

def main$()$:

# Calling load$\_$inventory$()$ should return a list of inventory items if

# inventory.dat is present. If that file is not present, it should

# return an empty list.

inventory $=$ load$\_$inventory$()$

display$\_$inventory$($inventory$)$

answer$\_$outer $=\text{'}\text{'}$

while answer$\_$outer.lower$()!=\text{'}$n$\text{'}$:

answer$\_$inner $=\text{'}\text{'}$

while answer$\_$inner not in $[\text{'}1\text{'},\text{'}2\text{'},\text{'}3\text{'}]$:

answer$\_$inner $=$ input$(\text{'}$What item type $(1-$Book, $2-$Game, $3-$DVD$)?\text{'})$

if answer$\_$inner not in $[\text{'}1\text{'},\text{'}2\text{'},\text{'}3\text{'}]$:

print$(\text{'}$Enter $1,2,$ or $3.\text{'})$

# TODO $-$ Create an appropriate object, ask the user for item input

# using the object's method, then append the object to the inventory

# list.

answer$\_$outer $=$ input$(\text{'}$Do you want to enter more items? $\text{'})$

display$\_$inventory$($inventory$)$

save$\_$inventory$($inventory$)$

def load$\_$inventory$()$:

inventory $=[]$

# TODO $-$ Attempt to load inventory data from a binary file named

# inventory.dat. If the file exists, load it into the inventory list.

# If the file does not exist, leave the inventory list empty.

return inventory

def save$\_$inventory$($inventory$)$:

# TODO $-$ Open a binary file named inventory.dat and dump the inventory

# list that has been passed in as a parameter to that file.

print$(\text{'}$Inventory$.$dat file was created.$\text{'})$

def display$\_$inventory$($inventory$)$:

print$()$

print$(\text{'}$Current Inventory'$)$

print$(\text{'}-----------------\text{'})$

# TODO $-$ Display the inventory items that are in the inventory list

# that was passed in as a parameter. If the list is empty, display

# "Inventory is empty."

print$(\text{'}-----------------\text{'})$

print$()$

main$()$