I wanted to change the animation time of the operator's animation and edited the keyframe value, but it doesn't take effect. I also executed the Update Keyframe and Apply to Keyframe Objects buttons, but there was no change. Is my approach wrong?
How are you testing the animation? If you set it as the idle animation then you won't see a difference, since that animation is played with a fixed duration of around 2s. I don't know if that can be changed at all.
If you intend to use the animation elsewhere then there is no need to adjust the duration. The start() method of the animation class let's you specify how fast the animation should play (factor of original time or scaled to fill target time) and how often it should be repeated. See the relevant documentation for more information.
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