Explain mixins

sass/utilities/mixins.sass

@@ -163,18 +163,6 @@
     &:#{$placeholder}-placeholder
       @content
 
-=replace($background, $width, $height)
-  background-color: $background
-  background-position: center center
-  background-repeat: no-repeat
-  background-size: $width $height
-  display: block
-  height: $height
-  outline: none
-  overflow: hidden
-  text-indent: -290486px
-  width: $width
-
 =unselectable
   -webkit-touch-callout: none
   -webkit-user-select: none