.fade {

opacity: 0;
transition: opacity .15s linear;

&.in {
  opacity: 1;
}

}

.collapse {

display: none;

&.in {
  display: block;
}
// tr&.in    { display: table-row; }
// tbody&.in { display: table-row-group; }

}

.collapsing {

position: relative;
height: 0;
overflow: hidden;
transition-timing-function: ease;
transition-duration: .35s;
transition-property: height;

}