title: How to make expandale only one row in ui-grid table
body: <p>I use ui-grid in my project.</p>
  <p>I am  using <a href="https://plnkr.co/edit/?p=preview" rel="nofollow noreferrer">expandable</a> feature in ui-grid.</p>
  <p>I need to make expandable only one row.</p>
  <p>For example, if I click on '+' sign on row number 5 and then I click on '+' sign on row number 2 the row number 5 have to be closed and row number 2 have to be expanded.</p>
  <p>Any idea how can I implement this behaviour in ui-grid?</p>
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