Check if this stuff does nothing :)

  >>> from zope.component import provideAdapter
  >>> from bda.cache import NullCacheManager
  >>> provideAdapter(NullCacheManager)

  >>> from bda.cache import ICacheManager
  >>> from bda.cache import NullCache
  >>> provider = NullCache()
  >>> provider.reset()
  >>> provider.size()
  0

  >>> provider.keys()
  Traceback (most recent call last):
      ...
  NotImplementedError: It's not possible to fetch keys from nothing

  >>> provider.values()
  Traceback (most recent call last):
      ...
  NotImplementedError: It's not possible to fetch values from nothing

  >>> provider.get('foo')
  >>> provider.__getitem__('foo')
  >>> provider.__setitem__('foo', object())
  >>> provider.__delitem__('foo')

  >>> manager = ICacheManager(provider)
  >>> manager.setTimeout(0)
  >>> def func():
  ...     return None
  >>> manager.getData(func, 'foo')
  >>> manager.get('foo')
  >>> manager.set('foo', object())
  >>> manager.rem('foo')
  >>> del manager['foo']