How do i mock a function being called inside the run method of a python threading.Thread inherenting class from the main thread

i have a function in a my_fuction.py

def my_funtion():    #do something    print("doing something")    return True 

i also have a a threading.Thread inhereting class called my_thread.py

from threading import Thread,Eventimport timeclass MyThread(Thread):    def __init__(self):        super().__init__(name="MyThread")        self.running = Event()    def run(self):        self.running.set()        while self.running.is_set():            return_value = my_function()            print(return_value)            time.sleep(3)

I want to test MyThread run method mocking my_function such that the run will not call the real my_function function but the mocked one

i have a unittest script for testing MyThread called test_my_thread.py and is as follows:

from my_thread import My_Threadimport unittestimport timefrom unittest.mock import Mock, patchdef mock_my_function():   print('didn't do anything')     return Falseclass TestMyThread(unittest.TestCase):    def setUp(self):        self.my_thread = MyThread()    def test_my_thread_run_method(self):        with patch("my_function.my_function", side_effect = mock_my_function) as mock_func:            self.my_thread.run() #hoping that this run method will call the my_function in its run method as mock_func            time.sleep(5)            self.my_thread.running.clear()            self.my_thread.join()            mock_func.assert_called_once() #This statement is failing which i assume is because the function was not patched in the MyThread.run method  were it i s used

How can I mock 'my_function' inside the run of MyThread or is there an alternative method of testing if it is running without actually running it (an alternative to mocking it) .