如何在django序列化程序中包含自定义函数？

from django.db import models
from rest_framework import serializers

# 假设有一个模型类
class MyModel(models.Model):
    name = models.CharField(max_length=100)
    age = models.IntegerField()

    def custom_function(self):
        # 自定义函数逻辑
        return f"{self.name} is {self.age} years old."

# 创建一个序列化器类
class MyModelSerializer(serializers.ModelSerializer):
    custom_field = serializers.SerializerMethodField()

    class Meta:
        model = MyModel
        fields = ('name', 'age', 'custom_field')

    def get_custom_field(self, obj):
        # 调用自定义函数并返回结果
        return obj.custom_function()

# 使用序列化器进行序列化
my_model = MyModel(name='John', age=25)
serializer = MyModelSerializer(my_model)
serialized_data = serializer.data