Django rest framework - Field level validation in serializer

Question

I have a serializer and I'm trying to add field level validation and I need to verify if some charfields of the serialize are empty or not, and if a boolean field is true or false.

I have this serializer but I never return an error even if Ficha_publicada is false

class PublicarSerializer(serializers.Serializer):

    Titulo = serializers.CharField(required=True)
    Ficha_publicada = serializers.BooleanField()

    def validate_Titulo(self, attrs, source):
        value = attrs[source]

        if not Ficha_publicada:
            raise serializers.ValidationError("Ficha no publicada")
        return attrs

    class Meta:
        model = Fichas

Answer 1

And for Django rest framework 3.0 and more recent versions:

def validate_Titulo(self, value):