Datetime数据类型未在视图烧瓶上呈现

from datetime import datetime
from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'your_database_uri'
db = SQLAlchemy(app)

class MyModel(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    datetime_field = db.Column(db.DateTime)

    def format_datetime(self):
        return self.datetime_field.strftime("%Y-%m-%d %H:%M:%S")

@app.route('/')
def index():
    data = MyModel.query.first()
    return render_template('index.html', data=data)

if __name__ == '__main__':
    app.run()