.collapse {
    display: none;
}

.collapse.in {
    display: block;
}
.collapsing {
    position: relative;
    height: 0;
    overflow: hidden;
    -webkit-transition-property: height, visibility;
    -o-transition-property: height, visibility;
    transition-property: height, visibility;
    -webkit-transition-duration: 0.35s;
    -o-transition-duration: 0.35s;
    transition-duration: 0.35s;
    -webkit-transition-timing-function: ease;
    -o-transition-timing-function: ease;
    transition-timing-function: ease;
}
