[1pt] TM#1 Implement methods

[Bhekisile]

add_item method in the Label class

• should take an instance of the Item class as an input
• should add the input item to the collection of items
• should add self as a property of the item object (by using the correct setter from the item object)

can_be_archived?() in the Book class

• should override the method from the parent class
• should return true if parent's method returns true OR if cover_state equals to "bad"
• otherwise, it should return false