Moral of "The Fox and the Snake"?

I am assembling a book for my young niece and nephew. What do you believe is the moral or lesson for a child, or children in this case, in the tale of "The Fox and the Snake"?

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The Fox and the Snake

A Snake, in crossing a river, was carried away by the current, but managed to wriggle on to a bundle of thorns, which was floating by, and was thus carried at a great rate down-stream. A Fox caught sight of it from the bank as it went whirling along, and called out, "Gad! The passenger fits the ship!"

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Thank you so much for your help!