在django序列化响应中，如何摆脱FileField的绝对路径(media_url前缀)？

from rest_framework import serializers

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

    def get_file_field(self, obj):
        # 获取文件的相对路径
        relative_path = obj.file_field.url
        return relative_path

    class Meta:
        model = MyModel
        fields = ('file_field', 'other_field')

from rest_framework import serializers

class RelativeFileField(serializers.Field):
    def to_representation(self, value):
        # 获取文件的相对路径
        relative_path = value.url
        return relative_path

class MySerializer(serializers.ModelSerializer):
    file_field = RelativeFileField()

    class Meta:
        model = MyModel
        fields = ('file_field', 'other_field')