title: How to fix "Warning: Use of the "var" keyword is deprecated"?
body: <p><a href="https://i.stack.imgur.com/5QbuP.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5QbuP.png" alt="enter image description here"></a></p>
  
  <p><br>
  I tried using <code>auto instructor = instructors[_address]</code> it gives me the error:<br>
  <code>DeclarationError: Identifier not found or not unique.</code></p>