Dump traces using cPickle.

def _finalize(self):
        """Dump traces using cPickle."""
        container = {}
        try:
            for name in self._traces:
                container[name] = self._traces[name]._trace
            container['_state_'] = self._state_

            file = open(self.filename, 'w+b')
            std_pickle.dump(container, file)
            file.close()
        except AttributeError:
            pass