title: How to set character limit in Text field ..?
body: <p>My py and xml files code show below and 
  i want to set 300 character limit for text field so what kind of changes needed in this code ?</p>
  
  <p>.py Code : </p>
  
  <p><code>description': fields.text('Description', required=True)</code></p>
  
  <p>.Xml Code : </p>
  
  <pre><code>&lt;field name="description"/&gt;
  </code></pre>