Python: Why is the multiprocessing lock shared among processes here?

I am trying to share a lock among processes. I understand that the way to share a lock is to pass it as an argument to the target function. However I found that even the approach below is working. I could not understand the way the processes are sharing this lock. Could anyone please explain?

import multiprocessing as mp
import time


class SampleClass:

    def __init__(self):
        self.lock = mp.Lock()
        self.jobs = []
        self.total_jobs = 10

    def test_run(self):
        for i in range(self.total_jobs):
            p = mp.Process(target=self.run_job, args=(i,))
            p.start()
            self.jobs.append(p)

        for p in self.jobs:
            p.join()

    def run_job(self, i):
        with self.lock:
            print('Sleeping in process {}'.format(i))
            time.sleep(5)


if __name__ == '__main__':
    t = SampleClass()
    t.test_run()