LockedSet.__contains__ returns wrong value

[xemage]

The code in Chapter 5 - lockedSet.py doesn't work propperly.

If you create a LockedSet object i.e.

z = LockedSet({1, 2, 3, 4})

and check if 2 is in z it will fail.
2 in z
returns
False
z.__contains__(2)
returns
None

The solution is to return the result of super(LockedSet, self).__contains__(elem)

def __contains__(self, elem):
     with self._lock:`
          return super(LockedSet, self).__contains__(elem)

Learning-Concurrency-in-Python/Chapter 05/lockSet.py

Line 16 in cd3f31b

def __contains__(self, elem):