SCSS mixins materializecss

Question

我正在尝试理解找到的materializecss mixins中的混音概念：http://materializecss.com/sass.html#mixins

如果您不想访问该页面，我认为您需要的那些：

animation($args)
animation-delay($delay)
animation-direction($direction)
animation-duration($duration)
animation-fill-mode($mode)
animation-iteration-count($count)
animation-name($name)
animation-play-state($state)
animation-timing-function($function)

所以说我正在使用Animate.css和ngAnimate，我有以下动画：

&.ng-enter {
  -webkit-animation: slideInLeft 1s;
  -moz-animation: slideInLeft 1s;
  -ms-animation: slideInLeft 1s;
  animation: slideInLeft 1s;
}
&.ng-leave {
  -webkit-animation: slideOutLeft 1s;
  -moz-animation: slideOutLeft 1s;
  -ms-animation: slideOutLeft 1s;
  animation: slideOutLeft 1s;
}

怎么会出现在mixin中呢？