title: Django DRF Serializer fields required conditionally
body: <p>I have a serializer which looks like this:</p>
  
  <pre><code>class MySerializer(serializers.Serializer):
      lat = serializers.FloatField(required=False)
      lng = serializers.FloatField(required=False)
  </code></pre>
  
  <p>I want to make sure that if a request comes with the 'lat' field, the 'lng' field will be mandatory and vice versa.</p>
  
  <p>I can do it with validate function but believe there is a better way of doing that.</p>