human
Solve the following python programming problem given the following code:
@ skipif (('__pypy__' in sys.builtin_module_names), reason = 'cannot test this on pypy') 
def test_no_memory_leak() : 
    def stub(v = '') : 
        pass 
class Foo (HasSignals) : 
        @ input 
        def parent(self, v) : 
            return v 
class Test (HasSignals) : 
        def __init__(self) : 
            self.foo = Foo (parent = self) 
            self.bar = Signal (stub, []) 
            HasSignals.__init__ (self) 
@ connect ('foo.title') 
        def title_len(self, v) : 
            return len (v) 
t = Test () 
    wt = weakref.ref (stub) 
    assert (sys.getrefcount (t) >= 3) 
    t.disconnect_signals () 
    t.foo.disconnect_signals () 
    t.bar.disconnect () 
    del t 
    assert (wt () is None) 

    
    

    Fix the buggy line: wt = weakref.ref (stub)
assistant
#Here is Python code to fix the buggy line: wt = weakref.

wt = weakref.ref (t)