In this homework assignment, you will write a program that prints out pairs of twin primes.

Since that may sound a bit overwhelming, we've broken up this process into a few steps for you.

First, write a function that determines whether or not a number is a prime number. As a

reminder, a prime number is a number that only has two factors: $1$ and itself. Note that $0,$

and $1$ are not prime numbers, and that $2$ is a prime number. You can not look up any

formulas or algorithms online to determine if a number is prime. You must use the

information above to write your own algorithm to determine if a number is prime.

Your function must have the following function header:

def is$\_$prime$($num$)$

As seen from the function header, the function should be named is$\_$prime and have

one parameter, num. This function should return a boolean that indicates whether or not

the number is prime. More specifically, if the number passed into this function is prime,

the function should return True. If the number passed into this function is not prime,

the function should return False.

After writing the is$\_$prime function, it's time to begin testing! Programmers often

write test cases to ensure that their code has been written correctly. While there are

useful Python frameworks designed specifically for testing $($such as unittest, which you

are welcome to read more about if you are interested$),$ we will not be using them in this

class $($due to time constraints that don't allow us to fit this into our curriculum$).$ Instead,

we will test our code by calling the functions we want to test in main, printing out the

functions' return values, and manually checking that the functions return what we

expect.

Write a main function that has three test cases for is$\_$prime. Each test case should call

is$\_$prime with a different argument and print out the return value of the function call.

Then, you should manually check that the return value is correct $($according to whether

the argument is actually prime or not$).$

A comprehensive group of test cases will test different paths of execution that the

is$\_$prime function may take. Put another way, all the test cases should not use just

prime numbers or just non$-$prime numbers as the arguments, since then your test cases

are never checking that the function behaves correctly in the other situation. We will be

grading this part of the assignment manually and checking that you wrote a

comprehensive group of test cases.

If your code fails the test cases, now is the time to go back and fix your is$\_$prime

function! You will use the is prime function in the next part of this assignment, so