Jupyter notebook never finishes processing using multiprocessing (Python 3)

It seems that the problem in Jupyter notebook as in different ide is the design feature. Therefore, we have to write the function (prime_factor) into a different file and import the module. Furthermore, we have to take care of the adjustments. For example, in my case, I have coded the function into a file known as defs.py

def prime_factor(value):
    factors = []
    for divisor in range(2, value-1):
        quotient, remainder = divmod(value, divisor)
        if not remainder:
            factors.extend(prime_factor(divisor))
            factors.extend(prime_factor(quotient))
            break
        else:
            factors = [value]
    return factors

Then in the jupyter notebook I wrote the following lines

import multiprocessing  
import random
from multiprocessing import Pool
import defs



if __name__ == '__main__':
    pool = Pool()
    to_factor = [ random.randint(100000, 50000000) for i in range(20)]
    results = pool.map(defs.prime_factor, to_factor)
    for value, factors in zip(to_factor, results):
        print("The factors of {} are {}".format(value, factors))

This solved my problem