def _clear_item_cache(self, i=None):
    if (i is not None):
        self._item_cache.pop(i, None)
    else:
        self._item_cache.clear()
def _clear_item_cache(self, i=None):
    if (i is not None):
        self._item_cache.pop(i, None)
    else:
        self._item_cache.clear()