'return cached value for the given key.  If no value
was yet cached or the value cannot be read, the specified
default is returned.
:param key: must be a ``/`` separated value. Usually the first
name is the name of your plugin or your application.
:param default: must be provided in case of a cache-miss or
invalid cache values.'

def get(self, key, default):

    path = self._getvaluepath(key)
    if path.check():
        try:
            with path.open('r') as f:
                return json.load(f)
        except ValueError:
            self.trace(('cache-invalid    at    %s' % (path,)))
    return default
