a.calls would have been 76 (due to the cached value of 0 having been
flushed by the 'b' instance).

Clear the cache with ``.cache_clear()``

>>> a.method.cache_clear()

Same for a method that hasn't yet been called.

>>> c = MyClass()
>>> c.method.cache_clear()

Another cache wrapper may be supplied:

>>> cache = functools.lru_cache(maxsize=2)
>>> MyClass.method2 = method_cache(lambda self: 3, cache_wrapper=cache)
>>> a = MyClass()
>>> a.method2()
3

Caution - do not subsequently wrap the method with another decorator, such
as ``@property``, which changes the semantics of the function.

See also
http://code.activestate.com/recipes/577452-a-memoize-decorator-for-instance-methods/
for another implementation and additional justification.
c