如何在 Django 序列化器响应中包含额外数据？

class MySerializer(serializers.ModelSerializer):
    extra_data = serializers.SerializerMethodField()

    class Meta:
        model = MyModel
        fields = ['field1', 'field2', 'extra_data']

    def get_extra_data(self, obj):
        return {'key': 'value'}

class MySerializer(serializers.ModelSerializer):
    class Meta:
        model = MyModel
        fields = ['field1', 'field2']

    def to_representation(self, instance):
        representation = super(MySerializer, self).to_representation(instance)
        representation['extra_data'] = {'key': 'value'}
        return representation

class MySerializer(serializers.ModelSerializer):
    extra_data = serializers.ReadOnlyField()

    class Meta:
        model = MyModel
        fields = ['field1', 'field2', 'extra_data']

    def get_extra_data(self, obj):
        return {'key': 'value'}