title: Django rest update one field
body: <p>I just got started with Django and got stuck on something that I believe should be simple, but I don't know how to do.</p>
  
  <p>I have a model like this one:</p>
  
  <pre><code>id = models.AutoField(primary_key=true)
  ...
  amount = models.IntegerField()
  ...
  </code></pre>
  
  <p>Basically, the user will give an amount and the model needs to be updated with the current amount + the amount that the user inputs.</p>
  
  <p>I use serializers to create new objects, but I don't really know how to use them to do this.</p>