title: Filter queryset for nested serializer in django rest framework
body: <p>Here is my view:</p>
  
  <pre><code>class SectorListAPI(generics.ListAPIView):
      queryset = SectorModel.objects.all()
      serializer_class = SectorSerializer
  </code></pre>
  
  <p>Here is my serializers:</p>
  
  <pre><code>class OrganizationSerializer(serializers.ModelSerializer):
  class Meta:
      model = GroupProfile
      fields = ('title','slug',)
  
  
  
  class DepartmentSerializer(serializers.ModelSerializer):
      organizations = OrganizationSerializer(many=True, read_only=True)
      class Meta:
          model = DepartmentModel
          fields = ('title', 'organizations',)
  
  
  class SectorSerializer(serializers.ModelSerializer):
      # title = serializers.CharField()
      departments = DepartmentSerializer(many=True, read_only=True)
  
      class Meta:
          model = SectorModel
          fields = ('title','departments',)
  </code></pre>
  
  <p>Look, here <strong>'SectorSerializer'</strong> is parent '<strong>DepartmentSerializer</strong>' is children and '<strong>OrganizationSerializer</strong>' is grand children serializer. Now in my view I can easily filter my queryset for '<strong>SectorModel</strong>'. But how can i filter on '<strong>GroupProfile</strong>' model.</p>