title: AWS WebSocket API Gateway Template Selection Expressions examples
body: <p>AWS API Gateway service page says that a Template Selection Expression can be used to implement a way to transform the request body. However the documentation for these selection expressions is very light and I haven't been able to find any examples.</p>
  
  <ol>
  <li>Where can I find examples of what these expressions look like?</li>
  <li>Where can I find what variables and options are available in these expressions?</li>
  </ol>