.fade {
  opacity: 0;
  transition: opacity 0.3s linear;
}
.fade.in {
  opacity: 1;
}
.collapse {
  display: none;
}
.collapse.in {
  display: block;
}
.collapsing {
  position: relative;
  height: 0;
  overflow: hidden;
  transition: height 0.35s ease;
}