Properties:

account$\_$number $-$ B$1,$ B$2,$ B$3$ assigned automatically by code in the $\_\_$init$\_\_$ method. Thus, the first bank account created gets B$1,$ the second B$2$ etc. Note that this is assigned automatically by code you write within the$\_\_$init$\_\_$ method for this class.

balance. An initial value for the balance is specified when the bank account object is created.

overdraft$\_$account $-$ The bank account object that provides overdraft protection, initially set to None. See set$\_$overdraft$\_$account method below.

Behavior $($or methods$)$:

$\_\_$init$\_\_$ initializer $($constructor$)$ for the bank account objects.

$\_\_$str$\_\_$ returns a string representation of an account in the form account number:balance. For example, B$1$:$200.$

deposit$($amount$)-$ deposit the specified amount into this bank account object

set$\_$overdraft$\_$account$($other$\_$account$)-$ Register other$\_$account as the overdraft account for this account. For example, a$1.$set$\_$overdraft$\_$account$($a$3)$ assigns account a$3$ as the overdraft account for account a$1.$

withdraw$($amount$)-$ withdraw the specified amount from this bank account object. See set$\_$overdraft$\_$account method above. If a withdrawal causes the balance of this account to become negative, a while loop must be used to repeatedly transfer money $($by using the transfer method$)$ from the overdraft account in $$50$ increments till the balance becomes positive. For example, if a withdrawal causes the balance to become $-76\mathrm{.}50,$ two transfers of $$50$ will be made to correct the negative balance.

transfer$($amount$,$ other$\_$account$)-$ transfer specified amount from this account to other$\_$account. For example, a$1.$transfer$(200,$ a$2)$ transfers $$200$ from account a$1$ to account a$2.$ This method must utilize the withdraw and deposit methods already defined in the class, i$.$e$.$ it must be implemented as a withdraw from one account followed by a deposit into the other.

Add a method to the class such that, assuming b$1$ and b$2$ are bank account objects, b$1+$ b$2$ returns a new bank account object whose balance is the sum of the balances of b$1$ and b$2.$