human
Solve the following python programming problem given the following code:
@ it ('can run run all its child ExampleGroups') 
def s(w) : 
    @ w.child.it ('succeeds') 
    def f(w) : 
        w.has_been_run = True 
w.parent.run (MockReporter ()) 
    assert f.worlds [0].has_been_run 

    
    

    Fix the buggy line: assert f.worlds [0].has_been_run
assistant
#Here is Python code to fix the buggy line: assert f.

assert w.worlds [0].has_been_run