csit.infra.dash/app/pal/static/sass/bootstrap/_transitions.scss

   1 .fade {
   2   @include transition($transition-fade);
   3
   4   &:not(.show) {
   5     opacity: 0;
   6   }
   7 }
   8
   9 // scss-docs-start collapse-classes
  10 .collapse {
  11   &:not(.show) {
  12     display: none;
  13   }
  14 }
  15
  16 .collapsing {
  17   height: 0;
  18   overflow: hidden;
  19   @include transition($transition-collapse);
  20
  21   &.collapse-horizontal {
  22     width: 0;
  23     height: auto;
  24     @include transition($transition-collapse-width);
  25   }
  26 }
  27 // scss-docs-end collapse-classes