Equivalent to pickle.load except that the HoloViews trees is
        restored appropriately.

def load(cls, filename):
        """
        Equivalent to pickle.load except that the HoloViews trees is
        restored appropriately.
        """
        cls.load_counter_offset = StoreOptions.id_offset()
        val = pickle.load(filename)
        cls.load_counter_offset = None
        return val