It provides two methods `Player:hasMark` and `Card:hasMark` for
determining if the player/card has the mark, which is more expressive
than `xxx:getMark` when only checking for the existence.
By the way, xxx:hasMark may directly determine a `Mark` in xxx.mark, for
which I added `table:hasKey` method in `util.lua`, but currently the
code still checks if the result of `xxx:getMark` is not 0.
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提供了`Player:hasMark`和`Card:hasMark`两个方法，用于在只需要判断是否有标记时可以直接使用`xxx:hasMark`，相比使用`xxx:getMark`而言更加表达代码的作用。
顺带一提，`xxx:hasMark`应该可以直接判断`Mark`是否在`xxx.mark`里，我在`util.lua`里添加了`table:hasKey`的方法用于判断，但目前的代码还是判断`xxx:getMark`的结果是否不为0。
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