ant-design/components/style/core/motion.less

@import '../mixins/motion';
@import 'motion/fade';
@import 'motion/move';
@import 'motion/other';
@import 'motion/slide';
@import 'motion/swing';
@import 'motion/zoom';

// For common/openAnimation
.ant-motion-collapse-legacy {
  overflow: hidden;
  &-active {
    transition: height 0.15s @ease-in-out, opacity 0.15s @ease-in-out !important;
  }
}

.ant-motion-collapse {
  overflow: hidden;
  transition: height 0.15s @ease-in-out, opacity 0.15s @ease-in-out !important;
}