In the retail store scenario, let's look at the portion of customer purchasing items from the retail store. Write a python program to implement the class diagram given below.Class Description: Bill class:Initialize static variable counter to $1000$generate$\_$bill$\_$amount$($item$\_$quantity,items$)$: Calculate bill amount based on the items purchased by the customerAccept a dictionary, item$\_$quantity which contains the item id $($key$)$ of the items purchased along with the quantity $($value$)$Accept a list, items which contains the list of Item objects available in the storeGenerate bill id starting from $1001$ prefixed by $"$B$"$ and initialize attribute, bill$\_$id$.$ Ex$."$B$1001","$B$1002"$ etc.Calculate bill amount based on the quantity and price of the items purchased by the customerSet attribute, bill$\_$amount with the calculated bill amountAssume that values in item$\_$quantity and items are always valid. Customer class:pays$\_$bill$($bill$)$: Pay bill based on the bill amountAccept Bill object which contains the details of the bill to be paid by the customerUpdate attribute, payment$\_$status to "Paid"Display customer name, bill id and bill amountNote: Perform case insensitive string comparisonFor testing:Create objects of Customer class, Item class and Bill classInvoke generate$\_$bill$\_$amount$($item$\_$quantity,items$)$ on Bill object by passing the dictionary containing item$\_$id and quantity of items purchased by the Customer and list of Item objectsInvoke pays$\_$bill$()$ on Customer object by passing the Bill object