title: How to preselect options in SELECT helper in web2py
body: <p>when creating multiple select input with SELECT, OPTION helpers, I want to preselect some options, I tried following  </p>
  
  <pre><code>OPTION('myOption', _value=val, value=[v1, v2])
  </code></pre>
  
  <p>extrapolating from the docs, but it does not work </p>