Line the pods on a cutting board. Place the tip of a sharp knife at the tip of the first vanilla bean. Lay the edge of the knife down the center of the bean, so that it aligns with the bean lengthwise. Press down to slice the bean open. Repeat with the remaining beans.  Some people skip the slicing step. Slicing the beans may make the extract more flavorful, but the tiny black seeds, or caviar, can give it a cloudy appearance. If you want to make sure the extract has great flavor but you don't want to cloud it with caviar, slice off the tips of the beans instead of slicing them in half. Put them directly into the bottle and close the cap tightly. Shake the bottle to distribute the contents. Place the bottle into a cool and dark place and leave the extract to infuse for two months. You'll notice the vodka change color to a golden-brownish color.  Don't store the vanilla in a warm or bright place, as it might spoil. Shake the bottle every so often to distribute the contents. Place a colander over a bowl and pour the vanilla extract through, so that the beans are caught in the colander. Use a funnel to transfer the extract to amber bottles, which protect the extract from sunlight so that it keeps for years on end.  If you prefer not to transfer the liquid, you can leave it in the vodka bottle, as long as it's stored in a cool, dark place. If the extract doesn't taste strong enough, leave it in the vodka bottle and add a few more vanilla beans. Let it sit for another few months before using.

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Write a summary of the previous text in Chinese:
切开豆荚。 把豆荚浸在一瓶伏特加中。 让豆荚在伏特加中充分浸泡。 把香草精装到茶色瓶中。