title: Passing a custom python function into a tornado template
body: <p>I want to write a custom function and pass it unto my tornado template fine.</p>
  
  <p>Like <code>def trimString(data): return data[0:20]</code> then push this into my tornado file.
  This should allow me trim strings.</p>
  
  <p>Is this possible?</p>
  
  <p>Thanks.</p>