如何比较控制器在django中保存的模型数据？

from myapp.models import MyModel

def compare_model_data(controller_data):
    # 获取数据库中对应的模型数据
    db_data = MyModel.objects.get(id=controller_data.id)

    # 创建一个字典来保存比较结果
    diff = {}

    # 比较每个字段的值
    if controller_data.field1 != db_data.field1:
        diff['field1'] = {
            'old_value': db_data.field1,
            'new_value': controller_data.field1
        }
    if controller_data.field2 != db_data.field2:
        diff['field2'] = {
            'old_value': db_data.field2,
            'new_value': controller_data.field2
        }
    # 比较关联模型的数据
    if controller_data.related_model.field3 != db_data.related_model.field3:
        diff['related_model.field3'] = {
            'old_value': db_data.related_model.field3,
            'new_value': controller_data.related_model.field3
        }

    return diff