title: How to make multiple level sections in UITableView in Swift 4
body: <p>How to make nested table (multiple level sections) in swift 4 like the below picture:
  <a href="https://i.stack.imgur.com/cDxbx.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/cDxbx.jpg" alt="enter image description here"></a></p>
  
  <p>A UITableView is designed to show just two levels (sections and rows), but I want to display more than two levels.</p>