在序列化程序django中获取外键的字段

from rest_framework import serializers
from myapp.models import MyModel, ForeignKeyModel

class ForeignKeySerializer(serializers.ModelSerializer):
    class Meta:
        model = ForeignKeyModel
        fields = ('id', 'name', 'other_fields')

class MyModelSerializer(serializers.ModelSerializer):
    foreign_key = serializers.SerializerMethodField()

    def get_foreign_key(self, instance):
        foreign_key_instance = instance.foreign_key
        if foreign_key_instance:
            return ForeignKeySerializer(foreign_key_instance).data
        return None

    class Meta:
        model = MyModel
        fields = ('id', 'name', 'foreign_key', 'other_fields')