title: Angular2 ng2-bootstrap collapse add transition/animation
body: <p>I m using this
  <a href="https://valor-software.com/ng2-bootstrap/#/collapse" rel="noreferrer">https://valor-software.com/ng2-bootstrap/#/collapse</a>
  and i would like to add an animation/transition on height 0 - auto but we all know that you can't add transition on height auto.
  I would like to add a slideToggle efect with a duration on it.
  tried to look for a solution for over 3 days...</p>
  
  <p>is there a known solution for this?</p>