12:34:56.78 >>> Call to main in File "/path/to_file.py", line 5
12:34:56.78    5 | def main():
12:34:56.78    6 |     f2()
    12:34:56.78 >>> Call to f2 in File "/path/to_file.py", line 9
    12:34:56.78    9 | def f2():
    12:34:56.78   10 |     f3()
        12:34:56.78 >>> Call to f4 in File "/path/to_file.py", line 18
        12:34:56.78   18 | def f4():
        12:34:56.78   19 |     f5()
            12:34:56.78 >>> Call to f5 in File "/path/to_file.py", line 22
            12:34:56.78   22 | def f5():
            12:34:56.78   23 |     pass
            12:34:56.78 <<< Return value from f5: None
        12:34:56.78   19 |     f5()
        12:34:56.78 <<< Return value from f4: None
    12:34:56.78   10 |     f3()
    12:34:56.78 <<< Return value from f2: None
12:34:56.78    6 |     f2()
12:34:56.78 <<< Return value from main: None