.collapse-operation-handler {
  text-align: center;
  color: white;
  background: #808D9A;
  line-height: 40px;
  width: 14px;
  height: 40px;
  position: absolute;
  top: 50%;
  left: 0;
  z-index: 120;
  border-radius: 5px 0px 0px 5px;
  cursor: pointer;
}
.collapse-operation-handler svg {
  -webkit-transition: -webkit-transform 0.4s;
  transition: -webkit-transform 0.4s;
  transition: transform 0.4s;
  transition: transform 0.4s, -webkit-transform 0.4s;
}