Why can't a leopard change his spots? A leopard cannot change his spots, can't he? Metaphor for what?

A leopard cannot change its spots "should be transformed from" a leopard cannot change its spots "and" a leopard cannot change its spots ",so it should be put forward by Feng Ming magnum in Wake Up the World! Chinese online dictionary: a leopard cannot change his spots. Jiāng shān y?g?I, b ě n x ng ná n y [explanation] The change of human nature is even more difficult in Hieyama. It is difficult to describe the change of human nature. [Source] [Example] A leopard cannot change his spots. B ǐ ng xing ná n yí [explanation] old saying. It is difficult to emphasize that people want to change their habits. [Source] Feng Ming Menglong's "Awakening the World" Volume 35: "As the saying goes,' a leopard cannot change its spots'." "[Example] A leopard cannot change his spots, but a leopard cannot change his spots. The change of Hieyama is even more difficult. It's hard to describe human nature. Feng Ming magnum's Wake Up the World, Volume 35, says: "Readers know something. As the saying goes, a leopard cannot change his spots. "